TMaxx operating instructions 52 - Great Hobbies

Traxxas CorporationCorporate Headquarters1100 Klein RoadPlano, Texas 75074Phone: 972-265-8000Toll-free 1-888-TRAXXASTraxxas U.K.P.O. Box 1128Winterbourne, Bristol BS17-2SHEnglandPhone: 44-117-956-1002Internetwww.Traxxas.comE-mail: support@Traxxas.comEntire contents ©2003 Traxxas Corporation. Traxxas, T-Maxx, TRX2.5, TQ-3, Top Fuel, EZ-Start, and ProGraphix are trademarks orregistered trademarks of Traxxas Corporation. Other brandnames and marks are the property of their respective holdersand are used only for purposes of identification. No part of thismanual may be reproduced or distributed in print or electronicmedia without the express written permission of Traxxas.0304092

IntroductionThank you for purchasing a Traxxas T-Maxx Nitro Monster Truck.Traxxas engineers have loaded your T-Maxx with innovativefeatures and incredible “drive-over-anything” performance thatyou won’t find anywhere else!Your T-Maxx combines automatic, two-speed shifting in forwardand reverse, with powerful four-wheel disc braking. Thepatented transmission design and three-channel TQ-3 radiosystem put these functions right at your fingertips.The new TRX 2.5 Racing Engine is the most powerful engine ofits size ever available in a Ready-To-Run truck. Two years ofengineering development and advanced design, along withthousands of hours of testing, puts the TRX 2.5 in a class byitself. Each part of the TRX 2.5—from the air filter on the slidecarburetor, to the tip on the dyno-tuned exhaust system—hasbeen carefully engineered to provide maximum power over thebroadest RPM range.Traxxas was the first with standard on-board electric starting.The new second generation EZ-Start has evolved into anincredibly advanced and reliable starting solution, featuringthermal protection for the motor and built-in diagnostics tomonitor the condition of the glow plug.Obviously, there’s much going on between the wheels of yourT-Maxx. In this manual, we’ll take you step-by-step through allnecessary set-up, break-in, tuning, and operating procedures.Even if you are an experienced R/C enthusiast, it isimportant for you to read and follow the procedures in thismanual. Pay particular attention to the fuel requirementsand break-in procedures. The advanced design of the TRX2.5 engine does not follow old-fashioned thinkingregarding fuel and break-in procedures.4 Before You Proceed5 Safety Precautions6 Tools, Suppliesand RequiredEquipment7 Anatomy of theT-Maxx8 Quick Start: GettingUp to Speed9 Gluing the Tires10 DecoratingYour T-Maxx11 The Traxxas TQ-3Radio System21 The TRX 2.5 Engine37 Driving the T-Maxx38 AdjustingYour T-Maxx42 Trouble ShootingYour T-Maxx44 Maintainingand StoringYour T-Maxx46 Index3

Before You ProceedCarefully read and follow all instructions in this and anyaccompanying materials to prevent serious damage to yourT-Maxx. Failure to follow these instructions will be consideredabuse and/or neglect.Before running your T-Maxx, look over this entire manual, andexamine the truck carefully. If for some reason you decide theT-Maxx is not what you wanted, then do not continue anyfurther. Your hobby dealer absolutely cannot accept aT-Maxx for return or exchange after it has been run.Warnings, helpful hints, and cross-referencesThroughout this manual, you’ll notice warnings and helpfulhints, identified by the icons below. Be sure to read them!An important warning about personal safety or avoidingdamage to your T-Maxx and related components.SupportIf you have any questions about your T-Maxx or its operation,call the Traxxas Technical Support line toll-free at:1-888-TRAXXAS (1-888-872-9927)Technical support is available Monday through Friday from8:30am to 9:00pm central time. Technical assistance is alsoavailable at www.Traxxas.com. You may also e-mail customersupport with your question at support@Traxxas.com. Jointhousands of Traxxas R/C enthusiasts in our online communityat ReadyToRun.orgTraxxas offers a full-service, on-site repair facility to handle anyof your Traxxas service needs. Maintenance and replacementparts may be purchased directly from Traxxas, or you can saveshipping and handling costs by purchasing them from yourlocal hobby dealer.Special advice from Traxxas to make things easier andmore fun.Refers you to a page with a related topic.4

Safety PrecautionsAll of us at Traxxas want you to safely enjoy your new T-Maxx.Operate your T-Maxx sensibly and with care, and it will beexciting, safe, and fun for you and those around you. Failure tooperate your T-Maxx in a safe and responsible manner mayresult in property damage and serious injury. The precautionsoutlined in this manual should be strictly followed to helpensure safe operation. You alone must see that the instructionsare followed and the precautions are adhered to.Important Points to RememberR/C fuel is dangerous and highly poisonous. Always follow alldirections and precautions printed on the fuel container.▼ ▼ ▼ ▼ ▼ ▼R/C fuel, especially when in a fuel dispensing bottle, maylook like a cool drink to a child. Keep all fuel out of the reachof children at all times. Do not place fuel containers on theground where children can get to them while you aredriving.R/C fuel is flammable. Never allow smoking, sparks, heat orflame in the presence of fuel or fuel vapors.The engine and exhaust system may become extremely hotduring use. Be careful not to touch the parts, especially whenrefueling or stopping the engine.Prolonged exposure to the engine exhaust can be harmful.Avoid breathing the engine exhaust. Always run your T-Maxxoutdoors, in a well-ventilated area. Never run the engineindoors.Don’t operate your T-Maxx at night, or anytime your line ofsight to the model may be obstructed or impaired in any way.▼ ▼ ▼ ▼Never operate your T-Maxx in crowds of people or busypedestrian areas. The T-Maxx is large and fast, and may causeinjury to those unaware of its presence.Because the T-Maxx is controlled by radio, it is subject toradio interference from many sources beyond your control.Since radio interference can cause momentary loss ofcontrol, always allow a safety margin in all directions aroundyour model to prevent collisions.The engine can be loud. If the noise makes youuncomfortable, wear ear protection. Be considerate of yourneighbors by not running your model early in the morningor late in the evening.Most importantly, use good common sense at all times.All instructionsand precautionsoutlined in thismanual should be strictlyfollowed to ensure safeoperation of your T-Maxx.The T-Maxx is notintended for useby those under 16years of age without thesupervision of aresponsible andknowledgeable adult.5

For more info onbatteries, see Usethe Right Batterieson page 13.A peak-detectingcharger isrecommended forbest performance andlongest battery life. Formore information, see Usethe Right Charger on page30.Tools, Supplies, and Required EquipmentYour T-Maxx comes with a set of specialty metric tools. You’llneed to purchase other items, available from your hobby dealer,to operate and maintain your model.Supplied ToolsYour T-Maxx comes with these specialty metric tools:1.5mm hex wrench2.0mm hex wrenchGlow plug (universal) wrenchOther Required Tools and SuppliesThin, hobby-quality cyanoacrylateinstant tire glue (often called CA glue)Safety glasses#2 Phillips screwdriver#1 Phillips screwdriverTRAXXASTurnbuckle wrenchesSmall flat-blade screwdriver (1/8 inch blade)Batteries12 AA alkaline batteries for the radio system7.2-volt NiCad battery pack for theEZ-Start starting systemNiCad battery chargerHobby knifeFilter oil (for the foam air filter)see page 27 for detailsAfter-run oil (WD-40) to protectthe engine from corrosionFuelTraxxas Top Fuel 10% quart - #5010 • 20% quart - #502010% gallon - #5060 • 20% gallon- #5070Fuel dispensing bottle (Traxxas part #5001)6

Anatomy of the T-MaxxFuel Tank LidShifting ServoPressure LineEZ-StartMotorFuel LineFuelTankSlipperClutchChassisSpurGearBatteryBoxOn/OffSwitchSteeringServoShiftRodSuspensionArm (upper)Bumper(Front)ShockTowerEZ-StartPlugSkid Plate(front)BumperMountCross-braceBodyMountPipeHangerDifferentialBulkheadHalf ShaftAirFilterAntennaMountTransmissionShock(Oil Damper)PipeReceiverBoxHeaderEnginesee pg. 20 for detailsAccess Plugfor Two SpeedAdjustmentAccess Plugfor Receiver CrystalThrottle/BrakeServoTurnbuckle7

The Quick StartGuide is notintended toreplace the full operatinginstructions available inthis manual. Please readthis entire manual forcomplete instructionson the proper use andmaintenance ofyour T-Maxx.8Quick Start: Getting up to SpeedThe following guide is an overview of theprocedures for getting your T-Maxx running,from opening the box to breaking in and tuning your engine.Refer to the pages indicated for details on each step. Look for theQuick Start logo on the bottom corners of Quick Start pages.1. Charge the battery pack • See sidebar, page 30The EZ-Start requires a fully charged 7.2-voltbattery pack (not included).2. Get the right fuel • See page 26Use Traxxas Top Fuel or consult with Traxxasbefore using other fuels.3. Glue the tires • See page 9Glue the tires to the rims to prevent the rimsfrom spinning inside the tires.4. Install the antenna • See page 15Install the antenna mast in the T-Maxx.5. Decal and Install the body • See page 10You will need to use the body during the break-inprocess so it’s best to decal it before you use it onthe truck.6. Install batteries in the transmitter • See page 13The T-Maxx requires 8 AA alkaline or rechargeablebatteries for the transmitter.7. Install batteries in the model • See page 14The T-Maxx requires 4 AA alkaline or rechargeablebatteries for the receiver.8. Install the EZ-Start battery • See page 30Install and connect the 7.2-volt battery pack inthe EZ-Start controller.9. Turn on the radio system • See page 18Make a habit of turning the transmitter on first, and off last.10. Check servo operation • See page 19Make sure the throttle, shifting, and steering servos areworking correctly.11. Range test the radio system • See page 20Follow this procedure to make sure your radio systemworks properly at a distance and that there is nointerference from outside sources.12. Fill the fuel tank • See page 26Use your fuel-dispensing bottle to fill the tank.13. Connect the EZ-Start to the model • See page 31Learn the proper way to use the EZ-Start electric startingsystem14. Start the engine • See page 32Learn to use the correct starting procedure for your TRX 2.5.15. Break-in your engine • See page 32Follow the break-in instructions exactly to ensure the bestperforming,longest-lasting engine.16. Tune your engine • See page 34Learn how to set the fuel mixture needles for optimumengine performance.17. Drive your T-Maxx • See page 37Learn how to use the two-speed and reverse functionson your T-Maxx18. Maintaining your T-Maxx • See page 44Follow these critical steps to maintain the performanceof your T-Maxx and keep it in excellent runningcondition.

Gluing The TiresThe tires on your T-Maxx must be glued to the rims using CA tireglue to prevent the rims from spinning inside the tires. You canglue the tires without removing the wheels from the truck. Forclarity, these instructions show the process with the wheelsremoved.1. Remove a wheel from theT-Maxx using the larger(8mm) end of the glow plug(universal) wrench.HubAxle Pin4. Reinstall the wheels, makingsure none of the axle pinshave fallen out from behindthe hex hubs.Always wear safetyglasses to preventglue fromsplattering into your eyes.The acetone infingernail polishremover willremove excess glue fromyour fingers.2. Use your thumb to push theside of the tire away from therim. Place one or two drops ofCA glue into the opening andrelease the tire. Capillaryaction will draw the gluearound the bead of the tire.For best resultswhile gluing, cleanthe bead of thetires and the grooves ofthe wheels with denaturedalcohol before applyingglue. This removes anymold release agent residuefrom the tires and wheels,providing a better bond.3. Repeat step two at four or five points around the rim, until thetire is completely secured to the rim. Turn the rim over andrepeat the process for the inside of the rim/tire. Repeat for theother 3 wheels.9

Decorating Your T-MaxxApplying The DecalsThe ProGraphix paintedbody is covered with aprotective film for shipping.You must remove this filmbefore applying any decals.To remove the film, lift acorner of the film andcarefully pull it off the bodyin one continuous piece.Your T-Maxx decals are diecutfor easy removal. Use ahobby knife to lift thecorner of a decal and lift itfrom the backing.Carefully position the decalover the desired locationand press one side on thebody. Pull the decal tightand use a finger to graduallysmooth out any air bubblesas you apply the decal.Look at the photos on the box for typical decal placement.10

The Traxxas TQ-3 Radio SystemYour T-Maxx (model 4910) is equipped with the TQ-3 RadioSystem. The TQ-3 is a 3-channel system that provides highpoweroutput up to a quarter mile and control for up to threeservos.T-Maxx WiringDiagramBlackNegativeRedPositiveAntennaThrottle TrimThrottle Neutral AdjustSteering WheelAntennaReceiverOn/OffSwitch4-CellBattery HolderSteering TrimReverse ShiftForward ShiftChannel 3Channel 2Channel 1BatteryChannel 1Steering ServoThrottle TriggerChannel 3Shifting ServoChannel 2Throttle ServoCH.3CH.2CH.1ServoReversingSwitchesPower SwitchBattery CompartmentPower Indicator11

Learn terms relatedto the TRX 2.5engine beginningon page 23.The Traxxas TQ-3 Radio SystemRadio System TerminologyPlease take a moment to familiarize yourself with these radiosystemterms. They will be used throughout this manual.Channel - The 27 MHz frequency band is divided into 6channels so that up to six models can be operatedsimultaneously. Each channel is referred to by its flag color andchannel number, as shown below.Channel Frequency Band Flag Color Traxxas Part No.1 26.995 Brown 20312 27.045 Red 20323 27.095 Orange 20334 27.145 Yellow 20345 27.195 Green 20356 27.255 Blue 2036Clearing your frequency - A routine, verbal check to make surenobody else in your area is operating on the same channel.Always clear your frequency by calling out your channelnumber before operating your model. Wait or move toanother area if your channel is already being used.Crystal (X-tal) - The plug-in device that determines whichchannel the radio system will operate on. For each channel,there are two crystals, one for the receiver and one for thetransmitter. Of those two crystals, the one marked with thelower number (.455 MHz lower) must be inserted into thereceiver.Frequency band - The radio frequency used by the transmitterto send signals to your T-Maxx. All Traxxas RTR models operateon a 27 MHz frequency band.Neutral position - The standing position that the servos seekwhen the transmitter controls are at the neutral setting.NiCad - Refers to rechargeable, nickel-cadmium batteries. Themost economical choice, since they may be recharged up to500 times.Receiver - The radio unit inside your T-Maxx that receivessignals from the transmitter and relays them to the servos.Servos - Small motor units in your T-Maxx that operate thethrottle, shifting, and steering mechanisms.Three-channel radio system - The TQ-3 radio system,consisting of the receiver, the transmitter, and the servos. Thesystem uses three channels: one to operate the throttle, one toshift the transmission, and one to operate the steering.Transmitter - The hand-held radio unit that sends throttle andsteering instructions to your T-Maxx.Trim - The fine-tuning adjustment of the neutral position of theservos, made by turning the throttle and steering trim knobson the face of the transmitter.12

The Traxxas TQ-3 Radio SystemInstalling Transmitter BatteriesYour TQ-3 transmitter uses 8 AA batteries. The batterycompartment is located at the base of the transmitter.CH.3CH.2CH.1Use the Right BatteriesYour transmitter and receiveruse AA batteries. Use newalkaline batteries, orrechargeable batteries such asNiCad or Ni-MH (nickel-metalhydride) batteries in yourtransmitter and receiver. Makesure rechargeable batteries arefully charged according to themanufacturer’s instructions.1. Remove the battery compartment door by pressing thetab and lifting the door up.2. Install the batteries in the correct orientation as indicatedin the battery compartment.3. Reinstall the battery door and snap it closed.4. Turn on the transmitter and check the power indicator fora solid red light.If the power indicator light flashes, then the transmitterbatteries are weak, discharged or possibly installed incorrectly.Replace with new or freshly charged batteries. The powerindicator light does not indicate the charge level of thereceiver batteries in the model.If you use rechargeablebatteries in your transmitter, beaware that when they begin tolose their charge, they losepower much more quickly thanregular alkaline batteries.Caution: Discontinuerunning your T-Maxx at thefirst sign of weak batteries(flashing red light) to avoidlosing control.If the power indicatordoesn’t light red, checkthe polarity of thebatteries. Check rechargeablebatteries for a full charge.13

The Traxxas TQ-3 Radio SystemDirect the batterywires through theslot in the batterycover. If the wires are notproperly routed, they maybecome broken or shorted,causing radio systemfailure and loss of control.Installing Receiver BatteriesThe radio receiver in your T-Maxx uses 4 AA batteries. The batteryholder for the receiver batteries is located underneath the batterycover. The battery cover can be identified by the on/off switch.1. Remove the battery cover by removing the two 3x10mmroundhead self-tapping screws from the cover.2. Remove the battery holder and install 4 AA alkaline batteries.Make careful note of the battery polarity by comparingagainst the diagrams in the battery holder.If you use rechargeablebatteries in your receiver,be aware that when theybegin to lose their charge,they lose power much morequickly than regularalkaline batteries. Signs ofweak receiver batteriesinclude sluggish steeringresponse and shortenedradio range. Caution:Discontinue running yourT-Maxx at the first sign ofweak batteries to avoidlosing control.On/OffSwitch4-cellbatteryholderIf the radio systemdoesn’t appear towork when thetransmitter and receiverswitches are turned on,check for correct batteryinstallation.143. Insert the battery holder into the battery cover.4. Reinstall the battery cover and secure with the screws(see sidebar!).

Setting Up the AntennaYou must install the antenna mast (tube) before you operateyour T-Maxx. You’ll find the plastic antenna tube and tip in thebag with your manuals and documentation.1. Locate the black antenna wire that exits the receiver cover.The T-Maxx receiver cover is mounted on the top of thechassis, near the front.2. Pull the wire straight with your fingers and then insert theend of the wire into one end of the antenna tube. Push thewire all the way through the antenna tube.3. Pull the remaining wire through the antenna tube, and theninsert the base of the antenna tube into the molded post ontop of the receiver cover.4. Fold the remaining antenna wire over the top of the tubeand secure it with the antenna tip.5. On the transmitter, always fully extend the telescopingantenna when running your T-Maxx. Make a habit of holdingthe transmitter so that the antenna points straight up.Antenna TipAntenna TubeThe Traxxas TQ-3 Radio SystemSpray a little windowcleaner on theantenna wire tomake it easier to pushthrough the antenna tube.Don’t shorten thelength of theantenna wire. Itslength is tuned to thefrequency band; cutting itcould severely shorten theradio system’s range.Don’t push thetransmitter antennadown from the top.Pull it down from thebottom, one segment at atime, to prevent binding andkinking the antenna mast.15

The Traxxas TQ-3 Radio SystemTQ-3 Radio System ControlsLEFTRIGHTSHIFTREVERSEACCELERATEBRAKENEUTRALSHIFTFORWARDCH.3CH.2CH.1CH.3CH.2CH.116

The Traxxas TQ-3 Radio SystemOther TQ-3 Radio System AdjustmentsIn addition to the electronic throttle and steering trim controls,your radio system features throttle neutral adjustment andservo reversing switches.Throttle Neutral AdjustmentThe throttle neutral adjustment is located on the transmitterface and controls the forward/reverse travel of the throttletrigger. Change the adjustment by pressing the button andsliding it to the desired position. There are two settingsavailable:50/50: Allows equal travel for both acceleration and braking.70/30: Allows more throttle travel (70%) and lessbrake travel (30%).50/50 is the required setting for the T-Maxx withthe TRX 2.5 racing engine.▼ ▼will roll freely). Do not use the throttle trim to raise or lower theengine idle speed. Make the idle speed adjustment on thecarburetor.Electronic Steering TrimThe electronic steering trim located on the face of thetransmitter adjusts the neutral (center) point of the steeringservo when the servo is at rest. Adjust this control to make themodel drive straight with no steering input at the wheel.Servo Reversing SwitchesThe servo reversing switches are located on the front of thetransmitter, next to the on/off switch. Moving a switch reversesthe direction of the corresponding servo.Each switch corresponds to a channel, as shown below. Forexample, if you turn the steering wheel to the right and yourfront wheels turn left, you would move the channel 1 switch tocorrect the servo direction. It may be necessary to adjust thecorresponding trim control after moving a switch.Channel Servo1 Steering2 Throttle and braking3 ShiftingCH.1CH.2CH.3Electronic Throttle TrimThe electronic throttle trim located on the face of thetransmitter adjusts the neutral (center) point of the throttleservo when the servo is at rest. This control has been preset foryou at the factory. If necessary, adjust the control so that thecarburetor is at idle, and the brakes are not applied (the model17

Remember, alwaysturn the TQ-3transmitter on firstand off last to avoiddamage to your T-Maxx.The Traxxas TQ-3 Radio SystemTQ-3 Radio System RulesEach time you prepare to run yourT-Maxx, you must clear your frequencyto be sure no one else in the area isusing the same channel as you.▼ ▼ ▼There are six possible channels,numbered 1 through 6. Each isrepresented by a color. Look at thecrystal plugged into the back of yourtransmitter to determine which channelyour truck is assigned to.Channel 1BrownChannel 2RedChannel 3OrangeChannel 4YellowChannel 5GreenChannel 6BlueAlways turn your TQ-3 transmitter on first and off last. Thisprocedure will help to prevent your T-Maxx from receivingstray signals from another transmitter, or other source, andrunning out of control.Always have the transmitter and receiver turned on beforeyou start the engine. Never turn the radio system off whilethe engine is running. The on/off switch in the model onlyturns the receiver on and off. It does not turn off the engine.▼Always use new or freshly charged batteries for the radiosystem. Weak batteries will limit the range of the radio signalbetween the receiver and the transmitter. Loss of the radiosignal can cause you to lose control of your T-Maxx.1 2 3CH.3CH.2CH.118

Using the TQ-3 Radio SystemThe TQ-3 Radio System was pre-adjusted at the factory. Theadjustment should be checked, before running the model, incase of movement during shipping. Here’s how:1. Fully extend the chrome antenna mast on the transmitterand turn the switch on. The red indicator light on thetransmitter should be solid red (not flashing).2. Turn on the receiver switch in the model. The switch islocated on the battery cover.3. Position the T-Maxx so that its front wheels are off theground.4. Turn the steering wheel on the transmitter back and forthand check for rapid operation of the steering servo. Also,check that the steering mechanism is not loose or binding. Ifthe steering operates slowly, check for weak receiverbatteries.5. When looking down at model, the front wheels should bepointing straight ahead. If the wheels are turned slightly tothe left or right, slowly adjust the steering trim control on thetransmitter until they are pointing straight ahead.The Traxxas TQ-3 Radio System6. Operate the throttle trigger on the transmitter and check forrapid operation of the throttle servo. When the throttletrigger is pulled back, the carburetor should open. When thethrottle trigger is pushed all the way forward, the brakeshould lock.7. Operate the shift button on the transmitter and check forrapid operation of the shifting servo. Push the shift buttondown for forward. The servo will push the transmission shiftrod into the transmission. Push the shift button up for reverseand the servo will pull the shift rod out of the transmission.8. Once adjustments are made, turn off the receiver on yourT-Maxx, followed by the handheld transmitter.ThrottleBrakeThrottle/BrakeServoWhen the engineis running, don’tuse the throttletrim on the transmitter toadjust the engine idlespeed. Instead, use theidle speed adjustment onthe carburetor.Because yourT-Maxx featureszero-scrub-radiussuspension and wide tires,the steering servo will notfully turn the front wheelswhen the vehicle is notmoving.0°0°ShiftingServoSteeringServoT-Maxx ServoOperation19

The Traxxas TQ-3 Radio SystemDon’t attempt tooperate yourT-Maxx if there areany problems with yourradio system or radiointerference at yourlocation.Range-Testing the TQ-3 Radio SystemBefore each running session with your T-Maxx, you should rangetestyour radio system to ensure that it operates properly.1. Turn on the radio system and check its operation as describedin the previous section (Using Your Radio System, pages 17- 19).2. Have friend hold the model with the engine off.3. Make sure your transmitter antenna is fully extended, and thenwalk away from the model with the transmitter until you reachthe farthest distance you plan to operate the model.4. Operate the controls on the transmitter once again to be surethat the model responds correctly.5. Do not attempt to operate the model if there is any problemwith the radio system or any external interference with yourradio signal at your location.20

The TRX 2.5 Racing EngineIntroductionThere’s nothing like the TRX 2.5 engine in your new T-Maxx.The TRX 2.5 engine is vastly superior to typical R/C engines andbelongs in the category of specialty high-performance racingengines. It’s the result of years of focused engineeringdevelopment, and thousands of hours of controlled testingand rigorous real-world running. It offers unprecedented powerand performance that turns ready-to-run into Ready-To-Race .The TRX 2.5 racing engine takes a total-system approach. Eachpart of the engine, from the air filter to the exhaust tip, iscarefully engineered to work in harmony with other enginecomponents. Each part complements the next, to extractmaximum power. The TRX 2.5 is designed to be tolerant ofvariations in tuning, and to run successfully through a widerange of variable atmospheric conditions, such as changes intemperature, humidity, and altitude.The TRX 2.5 is manufactured to exacting tolerances and requiresa specially-designed break-in procedure to accomplish the finalprecision fitting of the internal engine components. It is veryimportant that you follow the new break-in procedure as closelyas possible to achieve the best performance and longest lifefrom your TRX 2.5 racing engine. Old style break-in procedures,such as simply running the engine with a very rich fuel mixturefor the first 4 tanks of fuel, will not achieve the best results.Follow the steps in this manual.Traxxas stronglydiscourageschanging ormodifying any part of theTRX 2.5 engine. Old techtips and tricks that mayhave boosted the power ofother engines couldseriously diminish theperformance of the TRX 2.5.There’s more advancedthinking, development andtesting in the stock parts ofyour TRX 2.5 than in manyaftermarket manufacturer’sso-called performanceparts. The TRX 2.5 is alreadythe most powerful enginesin its class and simply willnot benefit from average,low-tech, aftermarket bolton performance items.A routine maintenance schedule is also required to keep theTRX 2.5 in top running condition. Cleaning the air filter aftereach hour of running is particularly important. Also it isextremely important to perform after-run maintenance on theengine to prevent corrosion from building up on the internalengine components (see page 44).21

The TRX 2.5 Racing EngineTRX 2.5 IllustratedAirFilterIdle SpeedScrewHead ProtectorHead (Cylinder head)EZ-StartDrive UnitHigh-Speed NeedleFuel IntakeAir IntakeCarburetorFlywheelClutchBellEZ-StartMotorCrankshaftGlow PlugWireGroundWireThrottleArmLow-SpeedNeedleEZ-StartPlugNegativeWireEngineMountCrankcaseEZ-StartControllerPositiveWireExhaustTipPressureLineFuel LinePipe22Fuel Tank

Terms to KnowYou’ll find these Nitro R/C engine terms throughout thissection of the manual..15 - .15 or “15” refers to the size of the engine. The TRX 2.5 is .15cubic inches or 2.5 cubic centimeters (cc). The name “TRX 2.5”is derived from the cc measurement.ABC - Abbreviation for aluminum, brass, and chrome. Refers toengine construction that consists of an aluminum piston thatslides in a chrome-plated brass sleeve. The TRX 2.5 uses ABCconstruction.Air filter - The air filter sits atop the carburetor and preventsharmful dust and dirt from entering the engine. Dirt ingestionis the number one cause of premature engine failure so theengine should never be run without the air filter in place.Big Block .15 - A .15 (2.5) engine that uses a larger crankcasesize and longer stroke than typical .15 engines. Generally onlyused for specific racing classes.Break-in - Break-in is the procedure for running a brand newengine according to specific instructions. This correctlyprepares the engine for normal running. The break-inprocedure can be different for different makes of engines.Follow the Traxxas directions for break-in exactly.Carb - Abbreviation for carburetor.Carburetor - The carburetor atomizes (mixes) the fuel with theair so that the engine can burn it. There are two types ofcarburetors, slide carbs and barrel carbs. The TRX 2.5 uses thesuperior slide carburetor design.Clean-out - Cleaning-out is a condition that occurs when theengine is accelerating and the fuel mixture becomessufficiently lean to allow the engine to continue into its upperRPM power band. Usually characterized by a noticeabledecrease in blue exhaust smoke and a dramatic increase inengine speed.Combustion chamber - The combustion chamber is machinedinto the bottom of the cylinder head. This is where the glowThe TRX 2.5 Racing Engineplug ignites the fuel. The shape of the combustion chamber isdesigned to promote more efficient burning of the fuel.Connecting rod - The connecting rod transfers the pistonmotion to the crankshaft. The TRX 2.5 racing engine uses a“knife-edged” connecting rod. The aerodynamic, sharpenededges allow it to “slice” through the pressurized air/fuelmixture inside the crankcase.Cooling fins - The cooling fins are molded into the cylinderhead and crankcase and cause heat to be drawn away fromthe engine. Heat is removed when it dissipates into the airpassing across the cooling fins. It is important to keep the finsclean of dirt and debris for maximum cooling efficiency.Crankcase - The engine “body” that contains all of the runningmechanical components.Crankshaft - The main shaft of the engine that contains therotating assembly.Cylinder head (head) - The finned aluminum part on top of theengine that is responsible for dissipating most of the engine’sheat. The combustion chamber is machined into the bottom ofthe head.Dyno - Abbreviation for dynamometer. A precise piece oftesting equipment that accurately measures engine powerand torque output over the engines entire RPM range.EZ-Start - Second generation Traxxas on-board electric startingsystem. The system consists of a hand held starter control unitand an on-board gearbox with an electric motor to spin theengine. The new EZ-Start contains many performance andreliability improvements over the first generation EZ-Start.Filter foam - The oiled foam element inside the air filterhousing. The filter foam in the TRX 2.5 must be thoroughlycleaned and re-oiled after every hour of run time.Fit - Usually refers to the fit of the piston and sleeve. If the fit istight, then the piston will feel very tight at top of the sleeveand the engine will have good sealing and compression. If thefit is loose, then compression will be low and the piston andsleeve should be replaced.Learn terms relatedto the TQ-3 RadioSystem on page 12.23

The TRX 2.5 Racing EngineFlame-out - Occurs when the engine stops running at highRPM. Usually the fault of an excessively lean fuel mixture orglow plug failure.Fuel - (10% 20%) The TRX 2.5 must have model engine fuel torun. Traxxas Top Fuel is recommended. Fuel is sold in quartsand gallons from hobby dealers. The 10 and 20% labelingrefers to the percentage amount of nitromethane contained inthe fuel (see “nitro percentage” definition).Fuel mixture - The ratio of fuel to air as determined by theneedle settings of the carburetor.Fuel tubing (fuel line) - The thick silicone tubing that carriesfuel from the fuel tank to the carburetor.Glow plug - The glow plug is located in the cylinder head at thetop of the combustion chamber. It contains a platinumelement that glows red hot when voltage is applied. When theengine is being started, the heat from the glow plug ignitesthe fuel mixture and starts the combustion process.Glow plug driver - This tool clips onto the glow plug andsupplies the required voltage to light the glow plug element. Itis also called an igniter. EZ-Start equipped engines do notrequire this separate tool.Header - The aluminum tube that connects the exhaust systemto the engine exhaust port. The length and diameter of theheader must be carefully selected to extract the most powerfrom the engine.High-speed needle - Adjusts the carburetors fuel/air mixture athigh RPM.Idle speed - The speed (RPMs) the engine runs at when thetransmitter’s throttle trigger is at neutral.Idle speed screw - Located on the carburetor body. This screwadjusts the idle RPM of the engine.Lean - A running condition where the engine is not gettingenough fuel (for the available air). Symptoms include engineoverheating, or the engine runs for a short time and thenstalls, particularly at high speed. This is a dangerouscondition that should be corrected immediately or it canruin your engine.Leaning the mixture - Turning either the high speed and/orlow-speed needle(s) clockwise to decrease the amount of fuelthe engine receives.Low-speed needle - Needle valve that controls the low-speedfuel mixture.Needle valve - Valve consisting of a tapered needle that closesagainst a corresponding seat to regulate fuel flow.Nitro - Abbreviation for nitro methane, a component of modelengine fuel that improves fuel combustion and power output.Nitro also refers to a class of RC powered by model enginesinstead of electric.Nitro content - The amount of nitro methane used in the fuel.Usually measured as a percentage of the total fuel volume.Traxxas engines are optimized to use 10-20% nitro. 30% nitromay be used for racing.Nitromethane - Nitro methane is a component in the fuel thatincreases power from the combustion process up to a point.Engines are generally optimized to use a range of nitrocontent for the best power.O-ring - Rubber “O”-shaped ring used as a sealing gasket.Pipe - Abbreviation for the tuned exhaust pipe on a nitroengine. See “Tuned Pipe” definition.Piston - The piston is the internal engine part that is attached tothe upper end of the connecting rod and moves up and downin the cylinder sleeve. The precise fit between the piston andthe sleeve creates a seal that allows engine to have therequired compression for combustion.Port - Ports are openings in the sleeve that allow atomized fuelto enter the combustion chamber and burned exhaust gassesto exit. The shape and location of the ports are a large factor incontrolling the engine timing and power output.24

The TRX 2.5 Racing EnginePriming - Manually causing fuel to move from the fuel tank upto the carburetor. This is sometimes necessary after the enginehas been sitting for a long period of time and all the fuel hasdrained back to the tank. On a Traxxas model this is done byholding your finger over the exhaust tip for one or twoseconds while the engine is starting.Punch - A term that refers to how quickly the model respondsto throttle input or how quickly it accelerates.Rich - A running condition where the engine is getting toomuch fuel for the available air. It is better to run an engineslightly rich to increase engine life. Excessively rich mixturescause the engine to have sluggish performance withexaggerated blue smoke and unburned fuel coming from theexhaust.RPM - Abbreviation for revolutions per minute (how many timesthe engine crankshaft spins in a minute).Sleeve - Internal engine part that contains the piston. Theprecise fit between the sleeve and the piston creates a sealthat allows engine to have the required compression forcombustion. The sleeve in a TRX engine is made of brass and isthen hard-chrome plated.Slide carburetor - The throttle on a slide carburetor closes andopens by sliding a barrel in and out of the carburetor body.This type of carburetor is preferred for performance usebecause it provides a less restrictive “straight-through” air paththan the barrel carburetor design.Stall - When the engine stops running, usually due to anincorrect fuel mixture setting or running out of fuel.Tuned pipe - The tuned exhaust pipe usually consists of aspecially-shaped metal or composite chamber with bafflesthat is designed to enhance the power output of the engine.Wear-in - Fitment process that occurs during engine break-inwhere internal engine parts develop an even more precisematched fit through actual use under controlledcircumstances.WOT - Abbreviation for wide-open throttle.25

You may use highernitro percentagesthan 20% in certaincircumstances. Call 1-888-TRAXXAS for moreinformation.26The TRX 2.5 Racing EngineThe FuelUse the Right FuelIt’s imperative that you use the correct fuel inyour TRX 2.5 for maximum performance andengine life. Traxxas Top Fuel should be usedto ensure correct engine lubrication,performance, and ease of tuning. Traxxas TopFuel has been proven in thousands of engines,so you can count on it every day for greatperformance.▼ ▼ ▼Top Fuel is the only fuel which is 100% certified for use inTraxxas engines.Traxxas Top Fuel is made with just the right balance of thehighest grade natural and synthetic lubricants to allowexcellent throttle response and the best top-endperformance, without sacrificing long-term durability.All of the components in the fuel are carefully selected fromthe best materials available and then custom blended tomatch the metallurgy and temperature characteristics ofTraxxas engines.You may use 10% or 20% nitro-content fuel. Use the samepercentage all the time; don’t switch back and forth between10% and 20% fuel. If you break-in your engine on 20% fuel, thenalways use 20% fuel.What about Other Fuels?Can other brands of fuel be used besides Top Fuel? There areother fuels that can provide satisfactory performance; howeverthere could be long-term costs in the form of decreased engineperformance, loss of tuning ease, and shorter engine life.Everyone has an opinion or a claim to make about fuel. Theengineering team at Traxxas spent over 2-years developing theTRX 2.5 engine. No one knows more about the specific fuelrequirements of Traxxas engines, than Traxxas engineers. Westrongly urge you not to take chances with your engineinvestment and use the Traxxas fuel made for the TRX 2.5.Handling the FuelFollow all directions and warnings on the fuel can.Keep the fuel tightly capped at all times. Some componentsin the fuel can evaporate very quickly and upset the balanceof the fuel.Do not store unused fuel in the fuel dispenser. Immediatelyreturn fresh unused fuel back into the fuel can.Do not mix old and new fuel. Never mix different brands offuel together.Store the fuel in a cool dry location, away from any source ofheat, ignition, or combustion.Read and follow the safety precautions on page 5in this manual.▼ ▼ ▼ ▼ ▼▼Filling the Fuel TankUse a fuel dispensing bottle (Traxxas TopFueler, part# 5001) to put fuel into theT-Maxx’s fuel tank. To fill the fuel bottle,squeeze the air out, insert the dispensertip into the fuel can, and release your gripon the bottle. As the bottleexpands, fuel will bedrawn into it.To fill your model flip upthe spring-loaded cap onthe fuel tank, insert the tipof the fuel bottle, andsqueeze to dispense thefuel. Fill the tank until thefuel level reaches the base of the filler neck. Close the fuel tanklid, making sure it closes tightly.Fuel Tank Seal AdjustmentThe rubber seal on the fuel tank is important to the function ofthe engine. The fuel tank is pressurized by the exhaust system toprovide reliable fuel flow. If the tank lid does not seal properly,an air leak will be created that can cause your engine to runerratically and be difficult to start. If necessary, the rubber O-ringtank seal can be adjusted for improved sealing by tighteningthe screw on the underside of the tank lid.

The Air FilterThe TRX 2.5 air filter is carefully designed to deliver maximumperformance while protecting your engine from dust and dirt.Use only the supplied filter. You will not improve engineperformance by switching to an aftermarket filter, and youmay risk engine damage due to poor filtration.The TRX 2.5 air filter assembly consists of 3 pieces:1. A rubber filter base2. A plastic housing consisting of a permanently assembledmesh cap and body3. An oiled foam elementYou must clean the filter after every hour of runtime, even if thefilter looks clean. Dust (which is often too fine to see) and dirtconstantly move through the filter anytime the engine isrunning. Even if you can’t see dirt on the filter, it is present insidethe foam after any amount of runtime. If you exceed therecommended cleaning intervals, your engine will be damaged.Engine damage or wear due to dirt ingestion is easy to detect,and one of the top causes of premature engine failure.Air Filter Cleaning Instructions1. Remove the air filter from thecarburetor bore by pullingthe entire filter firmly to theside to release it.Do not pull straight up2. Disassemble the filter. Pull therubber base out of the filterbody. With the base removed, the foam element is visible inthe bottom of the filter body. Pull out the foam element.The TRX 2.5 Racing Engine3. Clean the filter parts by thoroughly washing all three pieces ofthe filter assembly in hot soapy water (dishwashing detergentworks well). Repeat twice.4. Thoroughly dry the parts with a clean towel or compressed air.Remember to wear your safety glasses when working withcompressed air.5. Oil the foam element by saturating it with foam filter oil. Usethe supplied Traxxas filter oil (part# 5263) or a high-quality,special-purpose foam filter oil like what is used for highperformancemotorcycle and ATV engines.This type of filter oilis available at motorcycle pro-shops. If foam filter oil is notavailable, clean 30-40 weight motor oil can be substituted, butis not preferred. Never run the engine without a properlyoiled filter! Apply 30 drops of the Traxxas filter oil evenly tothe top, bottom and sides of the filter element (30 total dropsdivided among the 3 surfaces). Squeeze the filter elementrepeatedly to help spread the oil throughout. Squeeze theexcess oil from the foam.The filter element should be evenlycolored by the oil. Even color indicates that the oil is evenlydistributed. Note: Do not use the air filter oil for anythingother than the air filter. It is not meant to be a lubricant.6. Reassemble the filter and install it on the engine, making surethe rubber base fits securely on the carburetor with no gaps orair leaks.Clean your air filterafter every hour ofruntime to avoidengine damage, even if thefilter looks clean.If you usecompressed air todry your air filterassembly, wear safetyglasses and avoid directingcompressed air towardyour skin.27

See page 35 formore informationon how air densityaffects engine tuning.The TRX 2.5 Racing EngineThe CarburetorUnderstanding the Carburetor adjustmentsThe carburetor performs several functions. It controls theengine’s speed by restricting the intake of air and fuel into theengine. It atomizes the fuel (suspends the fuel droplets in theair) and also controls the air/fuel ratio of the mixture enteringthe engine (how much air for a given amount of fuel).FuelAirthe correct air/fuel ratio. Warmer air is less dense (fewer airmolecules) and therefore needs less fuel to maintain the correctair/fuel ratio. The tuning needles are there to adjust how muchfuel is made available for the carburetor to mix with theavailable air (atomization).Dense AirLess Dense Air28To help provide a better understanding of engine tuning andwhy it’s necessary, the following is a brief explanation of theair/fuel combustion process that takes place inside the engine.In order to create the cylinder pressure that results in power, theengine burns the air/fuel mixture. Both air and fuel, in correctamounts, are needed for proper combustion. It is thecarburetor’s job to mix the air and fuel together (atomize thefuel), in the correct proportion for the best possible combustion.This is the ideal air/fuel ratio. The ideal air/fuel ratio required forthe engine remains roughly constant. Due to variations inatmospheric conditions (temperature, humidity, altitude etc.)fuel flow adjustment valves (called fuel mixture needles) arerequired to meter the fuel and maintain the ideal air/fuel ratio inthese ever-changing conditions. For example, colder air is moredense (more air molecules) for a given volume of air andtherefore requires more fuel (more fuel molecules) to maintainThe Fuel Mixture NeedlesThe amount of fuel metered and atomized by the carburetor iscontrolled by the two mixture needles, the high-speed needleand the low-speed needle. The low-speed needle is used tometer the fuel used by the engine at idle and low RPM (partthrottle)engine speed. The high-speed needle is used to meterthe fuel when the throttle is open from part throttle to wideopenthrottle (WOT). Two needles on the TRX 2.5 provide precisecontrol of the air/fuel ratio across the engine’s entire RPM range.The maximum possible fuel flow is always controlled by thehigh-speed needle. It works like the main water valve on agarden hose. Turn it clockwise to close the valve, counterclockwiseto open it. When the throttle is at idle or partiallyopen, the low-speed needle again meters the fuel flow at theoutlet (needle seat) where the fuel enters the carburetor venturi.This second valve acts like the spray nozzle at the end of thegarden hose in our example. When you accelerate from idle, thethrottle opens and the low-speed needle is pulled away fromthe needle seat. This allows more fuel to flow with the increasedair flow. As the throttle is increased, the low-speed needle is

Water Valve(Controls Overall Flow)High Speed Needlepulled completely away from the needle seat leaving it fullyopen. At that point, fuel metering is entirely controlled by thehigh-speed needle. Again, using our water hose example, whenthe spray nozzle at the end of our garden hose is fully open,then the main water valve can be used to adjust how fast thewater flows.The engine’s performance is directly linked to the fuelmixture. Richening the fuel mixture increases the amount offuel in the air/fuel mixture ratio and leaning the fuel mixturedecreases the amount of fuel in the air/fuel mixture ratio.LeanWater Nozzle(Controls Fine Flow)Low Speed NeedleRich▼ ▼The TRX 2.5 Racing EngineSlightly lean fuel mixtures deliver stronger, more efficientcombustion and more power, but with less lubrication.Slightly rich fuel mixtures deliver cooler running and morelubrication but with slightly less power.Tuning the engine means finding the perfect balance betweenthe two; excellent power to meet your needs while maintaininggood lubrication for long engine life. The optimal fuel mixturesetting is rich to provide a safety margin against having a leancondition if some variable changes (such as the temperaturefrom one day to the next).General fuel mixture settings are measured by the number ofturns the needles are turned out from fully closed. The fuelmixture settings have been pre-set from the factory to typicalbreak-in settings. Do not readjust your carburetor from thefactory settings until after the engine is started and running,and you have been able to observe the engine running toassess what minor adjustments may be required to compensatefor fuel, temperature, and altitude. Adjustments are usuallymade in 1/8 or 1/16-turn increments.The Idle Speed AdjustmentThe idle speed screw controls the closed position of the throttleslide. When the throttle servo is in its neutral position, thethrottle slide should be stopped against the idle adjustmentscrew. Always use the idle speed adjusting screw to controlengine idle. Do not use the throttle trim on the transmitter toadjust idle speed. The idle speed should be set as low aspossible and still maintain reliable running.See Tuning YourTRX 2.5 engine forBest Performanceon page 34 for completeinformation on adjustingthe air/fuel mixture andidle speed.If your factorypreset carburetoradjustments havebeen tampered with, usethe following settings: setthe low-speed needle sothat the screw head is flushwith the end of the slide.Set the high-speed needleto 4 turns out from closed.Always use the factorysettings for initial starting.Only use these settingswhen the factory settingshave been lost.29

Use theRight ChargerThe most convenienttype of charger is an AC peakdetectingcharger that plugsdirectly into an AC walloutlet. It contains specialpeak-detection circuitry thatautomatically shuts thecharger off when the batteryis fully charged.If you’re using a 15-minutetimed charger, always fullydischarge the battery packbefore each charge. Somehigh mAh battery packs(1500 mAh or higher) requiremore than the standard 15minutes of charge time. If thebattery pack is cold after 15minutes of charging, addanother 5 minutes of chargetime. Closely monitor thebattery pack and stopcharging it when it begins tofeel warm to the touch. Neverleave a battery chargingunattended. Always followcharger manufacturer’sinstructions.The TRX 2.5 Racing EngineThe Traxxas EZ-Start Electric Starting SystemThe Traxxas EZ-Start brings the convenience of push-buttonelectric engine starting to your T-Maxx. The EZ-Start consists of ahandheld control unit and an on-board motorized starter.▼ ▼ ▼ ▼ ▼ ▼ ▼Power for the EZ-Start system comes from a 7.2-voltrechargeable NiCad battery pack installed in the handheldcontrol unit (battery not included).The engine glow plug is heated automatically by theEZ-Start system, eliminating the need to keep up with aseparate glow plug igniter.The voltage to the glow plug is kept constant, regardless ofthe load placed on the starter by the starter motor.The “Glow Plug” LED (light emitting diode) on the controlunit indicates the condition of the glow plug.The “Motor” LED indicates the status of the EZ-Start electricstarter motor.The cush drive mechanism in the drive unit preventsdamage to the gears caused by engine kickback.Smart Start protection circuitry prevents damage to themotor by cutting power if the load on the motor or otherelectronics exceeds safe limits.Installing the EZ-Start BatteryThe EZ-Start system requires a fully charged 7.2-volt NiCadbattery pack (not included). Use a charger (not included)designed for 7.2-volt battery packs. Charge the batteryaccording to the charger manufacturer’s directions.1. Press the tab in the end of the battery compartment doorto open2. Plug a fully charged 7.2-volt NiCad battery pack into theconnector inside.3. Twist the battery 2 or 3 times to twirl the battery plug wires.This helps hold the wire and battery in place when thebattery is placed in the compartment4. Place the battery into the compartment and press the wiressecurely into place.5. Slide the battery compartment door back on and lock theend tab.30

Using the EZ-StartYour EZ-Start controller plugs into a 4-prong receptacle in thecenter of the pickup bed on your T-Maxx. When the red buttonon the controller is depressed, the EZ-Start motor begins to spinthe engine, and power from the control unit heats the glowplug. Assuming all settings and preparations are correct, theengine should start almost immediately.Each of the two status indicatorLEDs on the handheld control unit,the Motor LED and the Glow PlugLED, should light green whilestarting. If either LED fails to lightwhile starting, there is a faultindicated with that function:▼ ▼MotorGlowPlugIf the Glow Plug LED fails tolight, the glow plug may be bad,or the glow plug wire may bedamaged or disconnected.If the Motor LED fails to lightand the starter fails to operate,then the EZ-Start is inprotection mode.MotorGlowPlugMotorGlowPlugMotorGlowPlugMotorGlowPlugThe TRX 2.5 Racing EngineProtection ModeThe EZ-Start uses Smart Start technology to monitor thecondition of the system and detect failures. The controllermonitors the load being placed on the EZ-Start motor. If theload becomes excessive, the system shuts off power to themotor to prevent costly damage to the motor and thecontroller. This may occur, for example, if the engine floods withfuel during starting. The starter spins at first but when excessivefuel in the combustion chamber begins to lock up the engine,the starter motor slows under the heavier load. This causes theprotection circuit to shut off the power to the motor. Allow atMotorGlowPlugleast 3 minutes for the starter motor to cool and the circuit toautomatically reset before continuing. Use the time to find andeliminate the condition that caused the excessive load on thestarter motor.MotorGlowPlugMotorGlowPlugWhen the EZ-Startcontroller is inprotection mode, waitat least three minutes beforeattempting to start theengine, to give the startermotor time to cool.It’s normal for yourEZ-Start controllerto become warmafter repeated use.See page 43for informationon clearing aflooded engine.31

See ImportantPoints to Rememberon page 5 for otherprecautions.Never run yourT-Maxx indoors.Since the TRX 2.5engine exhaust fumes areharmful, always run yourT-Maxx outdoors, in a wellventilatedarea.Your TRX 2.5engine doesn’tusually requirepriming. If you do need toprime your engine, watchthe fuel line carefully toavoid flooding your engine.See page 43 forinformation on clearing aflooded engine.Your carburetor ispre-set at thefactory to give thecorrect air-to-fuel ratio andidle speed for enginebreak-in. Do not adjust thecarburetor unless youobserve a poor runningcondition that requirescorrection.32The TRX 2.5 Racing EngineBreaking in Your TRX 2.5 Racing EngineThe TRX 2.5 uses a ringless, aluminum-brass-chrome (ABC)piston/sleeve construction.This type of engine design relies on avery precise running fit between the piston and sleeve for cylindersealing. Engine break-in is necessary to allow the piston andsleeve to develop an extremely precise fit and optimum cylindersealing. Therefore, proper engine break-in is critical to achievingthe fastest, most reliable engine performance.Allow yourself about 1 to 1 1 /2 hours to complete the break-inprocedure.The engine break-in period will take 5 tanks of fuel in aT-Maxx.The break-in time is not the time to impress your friendswith your new T-Maxx. You must wait until the engine is fullybroken in before attempting sustained high speed running.Patience and careful attention during break-in will reward you withthe best-performing TRX 2.5 possible.During break-in, your engine may appear to malfunction withsymptoms like stalling, inconsistent performance, and fouled glowplugs.These are simply the normal “break-in pains” enginessometimes go through.They will disappear once your engine isfully broken in. Many owners report not experiencing any of thesesymptoms with the TRX 2.5. We recommend to go ahead andreplace the glow plug with a new one after the engine break inprocedure.Engine Break-in ProcedureThe focus during break-in is to vary and limit the engine speed.This will be accomplished by accelerating and stopping at differentrates for the first 5 tanks of fuel. As the engine begins to break-in,the duration and intensity of the acceleration will graduallyincrease. Sustained high-speed running is not permitted until the6th tank of fuel. Perform the initial break-in on a large, flat, pavedsurface. Apply all throttle and braking actions gently. Abruptacceleration or braking could cause the engine to stallunnecessarily.▼ ▼Special break-in fuels are not recommended. Use the same fuelyou plan to use everyday.If possible, avoid breaking-in the engine on extremely hot orcold days.▼ ▼Pay careful attention to the fuel level. Do not allow the fuel tankto run completely empty. An extremely low fuel level causesthe mixture to run too lean.This could result in a burned glowplug or extremely high engine temperatures.Keep extra glow plugs handy (Traxxas part #3231).The break-inprocess can cause deposits to form on the plug leading to plugfailure.Follow the instructions exactly for each of the first 6 tanks of fuel.Starting Your TRX 2.5 Racing Engine for the First TimeBefore you start your TRX 2.5 engine for the first time, make sureyou have read all instructions and precautions in this manual. Payclose attention to the tank-by-tank break-in instructions in thenext section, and make sure you have read and understoodthem before you run your engine.Your engine must be at room temperature (70°F or 21° C) orabove the first time you start it.If it’s cooler than roomtemperature outside, keep your T-Maxx indoors until you’re readyto start it, then take it outside.1. Turn on the radio system according to the instructions on page18.2. Make sure the throttle is in the idle position.3. Connect the EZ-Start controller according to the instructions onpage 31.4. Press the starter button and watch for fuel moving through thefuel line up to the carburetor. Watch closely! The fuel moves veryfast. If the fuel doesn’t move through the line within 5 seconds,prime the engine by briefly (one or two seconds) covering theexhaust outlet until the fuel is just visible in the carburetor fuelline. Watch carefully! If the engine is primed too long, it willflood with fuel and stop turning.5. Once fuel reaches the carburetor, the engine should quickly startand idle.6.Disconnect the EZ-Start controller from the model.7.Proceed with the engine break-in.If your engine doesn’t start, see Troubleshooting Your T-Maxxon page 42.

The TRX 2.5 Racing EngineTank 11. Drive the model with the body off.2. Driving procedure: Gently pull the throttle trigger to 1/4throttle over a 2-second count. Then gently apply the brake tostop.Count the two seconds out while accelerating: onethousand one, one thousand two, and then stop. Operate thethrottle trigger as smoothly as you can. Repeat this starting andstopping procedure until the first tank of fuel is nearly empty.3. Look for thick blue smoke exiting the exhaust outlet. If there isno smoke, richen the high-speed needle 1/4 turn, by turning theneedle counterclockwise.4. When the fuel tank is nearly empty, shut off the engine bypinching the fuel line connected to the carburetor.5. Let the engine cool for 15 minutes.Note: If at any point the engine cuts out or stalls during gentleacceleration, richen the high-speed needle 1/4 turn by turning theneedle counterclockwise.Tank 21. From tank 2 forward, the T-Maxx should be driven with thebody on.2. Driving procedure: Gently pull the throttle trigger to 1/2throttle over a 2-second count. Then gently apply the brake tostop. Count the two seconds out while accelerating: onethousand one, one thousand two, and then stop. Repeat thisstarting and stopping procedure until the second tank of fuelis nearly empty.3. When the fuel tank is nearly empty, shut off the engine and let itcool for 15 minutes.Tank 31. Driving procedure: Gently pull the throttle trigger to 1/2throttle over a 3-second count. Then gently apply the braketo stop. Count the three seconds out while accelerating: onethousand one, one thousand two, one thousand three,and then stop. Repeat this starting and stoppingprocedure until the third tank of fuel is nearly empty.2. As the engine loosens, the idle speed may increaseand cause the model to try to creep forward whenstopped. Reduce the idle speed by turning the idleadjustment (see page 22) on the carburetorcounterclockwise.Tank12345Throttle1/41/21/2FullFull3. When the fuel tank is nearly empty, shut off the engine andrefuel. From here on out, you do not need to let the engine coolbetween tanks.Tank 41. Driving procedure: Gently pull the throttle trigger to fullthrottle over a 3-second count. Then gently apply the brake tostop. Count the three seconds out while accelerating: onethousand one, one thousand two, one thousand three, and thenstop. Repeat this starting and stopping procedure until thefourth tank of fuel is nearly empty.2. Apply the throttle gradually! Your finger should not reach fullthrottle until the end of the three-second count.The T-Maxx maytry to shift into second gear. If it does, reduce the throttle input.Do not let the T-Maxx shift out of first gear.3. Keep your driving smooth and consistent.4. When the fuel tank is nearly empty, shut off the engine andrefuel.Tank 51. Driving procedure: Gently pull the throttle trigger to fullthrottle over a 3-second count, hold for 2 more seconds, andthen gently apply the brake to stop. Count the five seconds outwhile accelerating. Repeat this starting and stoppingprocedure until the fifth tank of fuel is nearly empty.2. The model should be shifting into second gear. If it is not, tryturning the high-speed needle clockwise 1/8 turn to lean thefuel mixture slightly and test for shifting.3. When the fuel tank is nearly empty, shut off the engine andrefuel.Tank 6During the sixth tank of fuel, the engine can be tuned for generalperformance use. Proceed to the next section in this manual.Time2 Seconds2 Seconds3 Seconds3 Seconds5 SecondsCool15 Minutes15 Minutes---BodyOffOnOnOnOnNotesApply throttle gradually.Apply throttle gradually.Reduce idle speed if necessary.Do not allow shifting to high gear.Accelerate over 3 second count,hold for 2 seconds.As you gainexperience in thehobby, you maydiscover that many peoplehave differing opinions onwhat is the properprocedure to break-in amodel engine. Only use theTraxxas break-in procedure.Other break-in procedurescould result in a weak,damaged, or otherwise poorperforming engine. Theprocedure outlined herewas extensively tested andproven to yield betterperforming engines thanother “common” break-inmethods. Even if you haveyears of experience usingmodel engines, please donot ignore this caution!33

When adjusting thelow speed fuelmixture, it is veryimportant to make severalhigh-speed runs with theT-Maxx betweenadjustments to clear out anyexcess fuel. Perform thepinch test immediately after.If the engine is allowed toidle for a long period of time,it could “load up” with fueland give you an inaccuratemeasurement from yourpinch test.For yourconvenience, thelow-speed needlehas a positive stop thatprevents it from being overtightened and damaging theneedle and seat. This alsoprovides an easy way togauge how many turns outfrom closed the low-speedneedle adjustment is set to.When tuning forperformance, watchclosely to noticewhen there is no longer anyincrease in speed or powerwhen the high-speedmixture is lean. If you leanthe high-speed mixture tothe point that the enginecuts-out, hesitates, or stalls,you are well into the dangerzone and engine damage islikely. Richen the high-speedneedle 1/4 turn and retune.34The TRX 2.5 Racing EngineTuning Your TRX 2.5 Engine for Best PerformanceThe engine’s performance depends on the fuel mixture. Turn themixture needles clockwise to lean the fuel mixture andcounterclockwise to richen it. Leaning the fuel mixture willincrease engine power up to the engine’s mechanical limits.Never run the engine too lean (not enough fuel flow). Neverlean the engine until it begins to cut-out or stall. Leaning theengine beyond the safe allowable limits will result in poorperformance and almost certain engine damage. Indicationsof an overly lean mixture include:Cutting out or sudden loss of power during acceleration.Overheating (temperature beyond 270° F at the glow plug)Little or no blue smoke coming from the exhaust.If any of these conditions are present, stop immediately andrichen the high speed mixture 1/4 turn. The engine willprobably be slightly rich at that setting and you can then retunefor performance. Always tune for performance by starting richand moving leaner toward the ideal setting. Never try to tunefrom the lean side. There should always be a light stream of bluesmoke coming from the exhaust.Before you begin tuning, the engine should be warmed up to itsnormal operating temperature and running slightly rich. All finaltuning adjustments must be made to the engine at its normaloperating temperature. You can tell the engine is running richby noting any of the following:Sluggish acceleration with blue smoke coming fromthe exhaust.The T-Maxx may not shift into second gearThere is unburned fuel spraying from the exhaust tipLeaning the high-speed fuel mixture increases performance▼▼▼ ▼ ▼▼▼High-Speed Fuel Mixture AdjustmentWith the engine warm and running at a rich setting, graduallylean the high-speed fuel mixture in 1/16 turn increments. Makeseveral high-speed passes with the T-Maxx after eachadjustment to clear out the engine and note any change inperformance. The TRX-2.5 is extremely powerful. Remember toapply the throttle gradually to prevent wheelies or loss ofcontrol. Continue this procedure until one of the followingconditions exist:1. There is no longer any performance improvement2. The engine begins to cut out at high speed (Danger!)3. There is a sudden loss of power during acceleration (Danger!)4. The engine begins to overheat. Symptoms ofoverheating include:Steam or smoke coming from the engine (not exhaust)Hesitation or stalling during accelerationPopping or clattering sound when decelerating(detonation)Fluctuating idle speedTemperature measurement above 270° F at the glow plug▼▼ ▼▼▼If any one of the above conditions occurs, the fuel mixture isalready past the maximum safe lean setting. Richen the fuelmixture to the optimum setting by richening the high-speedneedle at least 1/8 turn counterclockwise and retest. This settingwill extend engine component life.

The TRX 2.5 Racing EngineLow-Speed Fuel Mixture AdjustmentThe low-speed mixture is always set after the high-speed needleis correctly adjusted. The low-speed mixture will be set using thepinch test.1. Once the engine is warm, do several high-speed runs toconfirm that the high-speed needle is set correctly.2. Bring the vehicle in and pinch closed the fuel line going intothe carburetor. The engine should run for 2-3 seconds, speedup, and then die.3. If the engine runs longer than 3 seconds, then lean thelow-speed needle 1/16 turn, make several more highspeedruns, and retest.4. If the engine dies immediately without speeding up, thenrichen the low-speed needle 1/8 turn, make several morehigh-speed runs, and retest.When the low-speed needle is set correctly, the engine’s throttleresponse should be very quick, possibly even to the point ofmaking it difficult to keep the T-Maxx from doing a wheeliewhen you accelerate!Idle Speed AdjustmentOnce the high and low-speed mixtures have been set, reducethe idle speed to the minimum reliable idle speed. Remember,this adjustment should be made while the engine is running atnormal operating temperature.1. Turn the throttle trim on the transmitter so that the brakesare applied. This ensures that the throttle slide is restingagainst the idle adjustment screw.If the...HumidityPressure (barometer)TemperatureAltitudeNitro %is..LowerHigherLowerHigherLowerHigherLowerHigherLowerHigherthen the air density is...Slightly more denseSlightly less denseLess denseMore denseMore denseLess denseMore denseLess dense2. If necessary, remove the air filter to gain access to the idleadjustment screw.3. Turn the screw counterclockwise to reduce the idlespeed, or clockwise to increase it. The idle speed shouldbe set as low as possible while still maintaining reliablerunning characteristics.4. Reset the throttle trim on the transmitterNote: If the idle speed is set too high it could prevent the T-Maxxfrom shifting between forward and reverse. If you experience this,simply reduce the idle speed.Fine-Tuning the CarburetorAfter fine-tuning your TRX 2.5 engine at the end of the break-inprocedure, no major adjustments to the fuel mixture are usuallynecessary. Make note of the temperature, humidity, andbarometric pressure at the time you finished fine tuning yourcarburetor. Current weather conditions can be found onlinefrom national websites, local TV news websites, and Television.This information will be considered your baseline setting.You may need to adjust your carburetor needles to compensatefor changes in temperature and barometric pressure (airdensity) from day to day. Generally, you’ll need to richen the fuelmixture when the weather is colder than your baselinetemperature and the air density is higher. Lean the fuel mixturewhen weather is warmer than your baseline temperature andthe air density is lower. The chart below provides generalguidelines on how weather conditions affect air density whenthey move higher or lower than your baseline setting (see page28 for detailed info on how air density affects mixture settings).adjust (correct) the fuel mixture to be...Slightly richerSlightly leanerLeanerRicherRicherLeanerRicherLeanerLeanerRicher35

The TRX 2.5 Racing EngineTuning The Engine By TemperatureThe following procedures require anoptional infrared temperature probeor on-board temperature gauge(Traxxas on-board digitaltemperature gauge, part#4090).Engine temperature can be used asan effective tuning aid when you understand the relationshipbetween engine temperature and ambient temperature.The engine operating temperature, when tuned for maximumperformance, will vary according to atmospheric conditions. Theatmospheric condition that has the most influence on enginetemperature is air temperature. Expect the engine temperatureto vary almost in direct proportion to atmospheric temperature.Assuming you tuned the engine for the same maximumperformance each day, the engine will run about twentydegrees hotter when it’s ninety degrees outside than it would inseventy-degree weather. For this reason, we cannot give you adefinitive temperature range that indicates the best possibleengine tuning.Even if it’s 100°F outside, you should be able to tune formaximum performance. Try to keep your engine from exceeding270°F when measured at the glow plug. If tuning for maximumperformance results in engine temperature exceeding 270°F, tryto increase airflow tothe engine by cuttingout the rear of thebody, windshield, andfront valance. If theengine temperaturestill cannot be keptbelow 270°F, richenthe high-speedneedle slightly.The temperature gauge can aid you in tuning by giving you arelative indication of how your adjustments are affecting theengine and by preventing you from exceeding maximumengine temperature. For example, as you lean the fuel mixture,the engine performance will increase along with thetemperature. If you continue to lean the fuel mixture and thetemperature increases but the engine performance does notchange, then you have exceeded the maximum safe leansetting.36

Driving the T-MaxxIntroductionYour TRX 2.5 engine is broken in,the fuel mixture is balanced, andthe idle is set…now it’s time tohave some fun! Thissection containsinstructions onforward/reverse shifting,and making adjustments toyour T-Maxx. Before you go on, here aresome important precautions to keep in mind.▼ ▼ ▼ ▼ ▼ ▼ ▼Don’t run your T-Maxx in water, mud, snow, or wet grass.It’s tempting, but water and mud are easily drawn throughthe air filter and will severely damage the engine. Smallamounts of moisture can cause electronics to fail and loss ofcontrol over your T-Maxx.The TRX 2.5 is extremely powerful. Remember to apply thethrottle gradually to prevent wheelies or loss of control.Don’t hold the T-Maxx off the ground and rev the engineexcessively with no load on the engine. This practice couldresult in internal engine damage. Avoid over revving theengine when the T-Maxx is airborne after a jump.Avoid excessive high-speed running for extended periods oftime or over long distances. This could cause the engine tobuild up enough speed to exceed maximum safe RPM limits.Don’t drive your T-Maxx with drive train damage of any kind.The engine could be damaged due to overloads on theengine caused by drivetrain friction, or over-revving causedby loose or missing parts.Don’t tow anything with your T-Maxx. The engine is cooledby airflow created by speed. Towing creates a high load onthe engine, and at the same time limits cooling of the enginedue to low vehicle speed.If your T-Maxx gets stuck, stop driving immediately. Move thevehicle and then continue driving.Forward and Reverse OperationForward and reverse gearsare selected with the shiftbutton located in thetransmitter handle grip. Theswitch is normally in thedown, or forward, position.To shift into reverse,bring your T-Maxx to acomplete stop and pushthe shift button up.Accelerate to engage the gear.▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼SHIFTREVERSESHIFTFORWARDTo return to forward gear, repeat the same procedure andmove the shift button down.The T-Maxx will not shift between forward and reverseunless the engine is at idle. If it will not shift, then refer to thetroubleshooting section on page 42.Driving TipsMonster trucks by design have a high center of gravity thatrequires a different driving technique. To prevent rollovers,slow down as you approach turns and then apply strongthrottle through the turns. This technique will help theT-Maxx grab the surface and turn sharper.Do not apply brakes and turn the wheel at the same time.You could tip the truck over.When jumping, apply some throttle while the T-Maxx is inthe air to keep the truck’s nose up and land level on all 4wheels. Be careful not to over-rev the engine or land at fullthrottle. Either could seriously damage your T-Maxx. If thenose of the truck is too high, then quickly tap the brake tolevel the truck in the air..Drive over large obstacles (such as curbs and rocks) at anangle, instead of head on. This will allow the suspension toarticulate and absorb the impact much easier.Even though the T-Maxx is capable of full top speed inreverse, it is very difficult to control while driving in reverse.Limit your reverse speed to prevent crashing or flippingyour T-Maxx.37

38Adjusting Your T-MaxxOnce you become familiar with driving your T-Maxx, you mightneed to make adjustments for better driving performance.Adjusting the Slipper ClutchThe T-Maxx features an adjustable slipper clutch on the spurgear to help protect the drive train from sudden shock loads(such as landing off of jumps with the engine at full throttle).Under normal conditions the slipper clutch should not slip.Before adjusting the slipper clutch, turn the model off. Donot adjust the slipper clutch while the engine is running.Use the supplied glow plug (universal) wrench to tighten theslipper nut (clockwise) until it stops, and then back the nut out1/4 of a turn. If you notice any decrease in performance aftermaking changes to the slipper clutch adjustment, then it maybe too loose. The slipper must not be allowed to slip duringnormal acceleration or the slipper could be damaged.Adjusting the Two-Speed TransmissionThe T-Maxx comes equipped with a two-speed transmission.When the shift point on the transmission is adjusted correctly, itwill maximize acceleration and improve drivability. If necessary,use the supplied 2.0mm hex wrench to adjust the shift point.1. Stop the engine.2. Remove the large rubber plug from the transmission housing.3. Look into the hole in thetransmission housingand rotate the spur gearuntil the access hole inthe aluminum drumis visible.4. Once the access hole isvisible, hold the spurgear and use your fingerto turn the primary gearHOLDPrimary Gear Shaftshaft which extends from the transmission housing counterclockwise.Note that you will see two set screws pass underthe access hole. As you turn theprimary gear shaft counterclockwise,the first set screwholds the two-speed mechanismto the shaft. Do not loosen thisscrew. The second set screw isthe adjustment screw.5. Insert the 2.0 hex wrenchthrough the clutch drum andinto the adjustment set screw.6. Turn the adjustment screw 1/8 turn clockwise to raise theshift point (later shifts). Be careful not to over tighten theadjustment screw or you may damage the tension spring.Do not make constantadjustments or you will loosenthe screw’s locking device.7. Turn the adjustment screw 1/8turn counter-clockwise to lowerthe shift point (earlier shifts).Be careful not to loosen theadjustment screw too much oryou may cause the screw andspring to fall out (requiring majordisassembly and repair).8. Use 1/8 turn increments to find(Viewed from front of truck.)the approximate, desired shift point.9. Check performance by running a test lap aftereach adjustment.10. Use 1/16 turn increments to fine-tune the shift point.11. Be sure to reinstall the access plug to prevent dirt fromentering the transmission.

Adjusting the Toe-inYour T-Maxx comes from the factory with zero degrees of toe-inin the front, and one degree of toe-in in the rear.You can adjustthe toe-in on the front and rear of the truck. Set the steering trimon your transmitter to neutral. Now, adjust your steeringturnbuckles so that both front wheels are pointing straight aheadand are parallel to each other (0 degrees toe-in).This will ensurethe same amount of steering in both directions. Adjust the reartoe control links so that the rear wheels have 1˚ of toe-in.0°0°Unscrewing the bottom camber pivot ball with a 2.5mm hexwrench will increase the wheel’s negative camber. You shouldnot adjust the top pivot ball; unscrewing it will increase positivecamber and will also change the wheel’s toe-in.-1° -1°Adjusting Your T-MaxxFactory toe-insettings can beachieved byinstalling the rod ends onthe turnbuckles until theybottom out against theshoulder. If you desiremore toe-out, the tips ofthe rod ends must betrimmed to allow them toscrew down further ontothe turnbuckle threads.1°Adjusting the CamberTwo pivot balls are accessiblethrough the spokes of each of thewheels on your T-Maxx. From thefactory, the pivot balls arecompletely tightened into thesuspension arms, which give eachof the wheels –1˚ of camber.1°Fine Tuning the Oil DampersThe eight oil dampers (shocks) on yourT-Maxx have tremendous influence onits handling. Whenever you rebuild yourshocks, or make any changes to thepistons, springs or oil, always do itcarefully and in sets (front or rear).Piston head selection depends on therange of oil viscosities that you haveavailable. For example, using a two-holepiston with lightweight oil will give youthe same damping as a three-holepiston with heavier oil. We recommendusing two-hole pistons with a range ofoil viscosities from 10W to 40W(available from your hobby shop). Thethinner viscosity oils (30W or less) flowwith less resistance and provide lessdamping, while thicker oils providemore dampening. Use only 100% pure silicone shock oil toprolong seal life. From the factory, the T-Maxx uses 30W oil.The ride height for the T-Maxx can be adjusted by adding orremoving the clip-on spring pre-load spacers. Note that changesin ride height will occur when changes in shock angle or springrates are made. You can compensate for ride height changes bychanging the pre-load spacers on the shocks39

For easier access tothe rear-most shockmounting screw,remove the one end of therear turnbuckle. In the front,remove the suspension pinfrom the lower frontsuspension arm to gaineasier access to the lowershock mounting screws.40Adjusting Your T-MaxxAdjusting the suspensionThe T-Maxx has adjustable suspension so that it may beoptimized for different kinds of terrain and driving styles.Caster AdjustmentThe T-Maxx offers the ability to adjust the caster angle of thefront suspension. Caster adjustment may be used to influencethe understeer/oversteer handling characteristics of the T-Maxx.Increasing the caster angle will increase the tendency of thetruck to oversteer (less traction on the rear tires, more tractionon the front tires), while decreasing the caster angle will causethe truck to have a tendency to understeer (push in the turns).This effect becomes more pronounced at higher steering anglesand higher spring rates. Caster is adjusted by repositioning theshims on the pivot point of the upper suspension arms.The stock caster setting is 7-degrees with one shim at each endof the arm. Reduce the caster angle to 4-degrees by removingthe rear shim and inserting it next to the front shim. The casterangle can be increased to 10-degrees by removing the frontshim and inserting it next to the rear shim.Caster adjustment shims (2 Front)Ground plane4°VerticalCaster adjustment shims (1 Front, 1 Rear)Ground plane7°Vertical10°Ground planeCaster adjustment shims (2 Rear)VerticalShock Mounting PositionsBig bumps and rough terrain require a softer suspension withthe maximum possible suspension travel and ride height.Racing on a prepared track or on-road use requires a lower rideheight and firmer, more progressive suspension settings. Themore progressive suspension settings help reduce body roll(increased roll stiffness), dive during braking, and squat duringacceleration.The innermost upper shock mounting position (0) on the shocktower is intended for use with the first generation T-Maxxsuspension arms. With thesecond generation arms(2.5-powered T-Maxx),position (0) can be used fortuning with the inner pair oflower shock mountingpositions on the arm (1,2).It is not compatible withlower shock mountingpositions 3 and 4 on thesecond generation (2.5-powered T-Maxx) arms.Upper shock mountingposition (A) shouldgenerally be used withlower shock mountingpositions 1 and 2. Upper shock mounting position (B) should begenerally be used with lower shock mounting positions 3 and4.Other combinations may be used to achieve individualizedsuspension settings.Lower Shock Mounting PositionsIn the out-of-the-box configuration, the shocks are installed inposition (A) on the shock tower and position (2) on the lowersuspension arm. This setting allows for moderate suspensiontravel and ride height. The more vertical position of the shocksallows for lower shock progression and the soft, plush feel that’scharacteristic of the T-Maxx.The outer pair of holes on the lower suspension arm should beused to lower the ride height of the T-Maxx, and increase thespring force (at the wheel). This setting will improve high-speedcornering on smoother terrain by lowering the center of gravityand providing a firmer suspension feel. Body roll, brake dive, andsquat will be reduced.Spring rate (at the wheel) increases as the lower shockmounting position is moved from position (1) to position (4).This is equivalent to using stiffer springs. Use higher spring ratesettings for flatter terrain with smaller and fewer bumps, andlower spring rate settings for bigger bumps.

Adjusting Your T-MaxxRide height decreases as the lower shock mounting position ismoved from position (1) to position (4). Each pair of lower shockmounting holes (1,2 and 3,4) has equal ride height. Use lowerride height for high-speed cornering and flat terrain, and whenracing on relatively smooth tracks. Increase the ride height forrougher terrain and tracks.Upper Shock Mounting PositionsThe upper shock mounting positions will have suspensioneffects opposite from the lower shock mounting positions.Spring rate (at the wheel), increases as the upper shockmounting position is moved from position (A) to position (B).Ride height is not affected by changes in the upper shockmounting position.Use the chart below to see the effect of the various shockmounting positions. The horizontal length of the lines indicatesthe amount of suspension travel. The angle or slope of the linesindicates the spring rate (at the wheel).Wheel Force (lb)2.521.51Lower Mount 1, Upper Mount 0Lower Mount 2, Upper Mount 0Lower Mount 1, Upper Mount ALower Mount 2, Upper Mount ALower Mount 3, Upper Mount ALower Mount 4, Upper Mount ALower Mount 1, Upper Mount BLower Mount 2, Upper Mount BLower Mount 3, Upper Mount BLower Mount 4, Upper Mount BWheel Force vs. Wheel TravelMore FirmLess FirmLower Mount 4Lower Mount 3Lower Mount 2Lower Mount 10.500 10 20 30 40 5060 70 80 90 100Wheel Travel (mm)41

Troubleshooting Your T-MaxxThe following section addresses some very basic engine andradio questions you may have about your T-Maxx. Most questionsarise from simple user errors or minor adjustments that are easyto correct. If you can’t find a solution for your T-Maxx here, thenvisit our Web site at www.traxxas.com and click on the CustomerSupport menu.There you will find a much more extensive anddetailed online troubleshooting area. In addition, you may callTraxxas Customer Service at 1-888-TRAXXAS (outside UScall 972-265-8000).Radio system does not work properly:If the power light on the transmitter does not come on, checkfor proper battery installation and that the batteries are newand/or fully charged. If the power light is blinking, then thetransmitter batteries are weak and should be replaced. Seepage 13 for more details.If the transmitter light is on but the radio is still notresponding, check for proper installation of the receiverbatteries and that the batteries are new and/or fully charged.Check to make sure the on/off switch on the model is in theon position. Finally, if there is still no response check the redand black wires that connect the battery pack to the “batt”terminal on the receiver (you will have to remove the receivercover). Make sure the wires are not pinched or damaged andthat the plug is secure in the receiver. See page 14 for moredetails.▼ ▼ ▼ ▼Short radio range:If the radio range appears short, then first check to make surethe transmitter antenna is fully extended and that theantenna in the T-Maxx is in place and has not been cut ordamaged. Next, make sure the batteries are all fully charged.Finally, if you are still experiencing short range, try a differentlocation. Sometimes there can be interference from varioussources that can cause your radio to malfunction.The transmission is stuck in neutral(neither forward or reverse is engaged):Do not rev the engine. Revving the engine with no load cancause serious internal damage to the engine, such as a brokenconnecting rod. Move the shift button back and forth until agear is selected.The transmission will not shift between forward and reverse:Reduce the engine idle speed.The engine idle speed shouldbe set as low as possible and still allow reliable running. If theidle speed is too high, the T-Maxx will not shift.Unload the driveline. If the T-Maxx driveline is heavily loaded,as it might be when stuck on an incline or against an object, itmay not shift into reverse.▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼Engine will not spin (EZ-Start will not turn the engine):If neither LED on the controller lights, the EZ-Start batterycould be discharged or improperly connected. Inspect andrecharge if necessary.If the glow plug LED lights and the motor LED does not, thenthe EZ-Start controller is in protection mode. Allow thecontroller to cool for at least three minutes.The circuitryshould automatically reset.Check to make sure the wires are connected to the EZ-Startmotor in the T-Maxx.The red wire should connect to thepositive motor terminal, indicated by a red dot next to theterminal.The engine could be flooded. If too much fuel accumulates inthe combustion chamber at start up, the engine willhydraulically lock. Follow the procedure on page 43 forclearing a flooded engine.Check for binding at the engine flywheel. If you are not able toturn the engine by hand, the engine could be flooded, therecould be binding in the clutch system, or there could beinternal engine damage. (Note: It is normal for the engine tobe extremely tight and hard to turn when the piston reachesthe top of the compression stroke.)The T-Maxx shudders or jerks during acceleration:This occurs when the T-Maxx is accelerated slowly.Theengagement pawls inside the transmission use centrifugalforce to operate.The engine must be turning above a certainRPM before the pawls will swing out and engage. If the engineis run at just below engagement RPM the truck will appear to42

shudder when taking off. It is most apparent during thebreak-in process when you are driving in a gentle manner.Accelerating slightly faster will virtually eliminate anyvisible shuddering.Engine spins but will not start:If the engine is spinning but will not start, first check to makesure that both the motor and glow plug LEDs on the EZ-Startcontroller light when the button is depressed. If the glowplug LED does not light, make sure the blue glow plug wire istightly connected and is not damaged in any way. If the wireis good, then replace the glow plug. It is normal for glowplugs to require periodic replacement. Only use Traxxasheavy-duty long glow plugs (part #3231).Check to make sure the fuel is getting to the carburetor.Remove the fuel line where it connects to the carburetor tosee if there is fuel in it. If not, you may need to prime theengine. Reconnect the fuel line and then refer to page 32 forinstructions on priming the engine.Check your fuel mixture settings. It may be necessary toadjust the fuel mixture if the outside temperature orbarometric pressure has changed significantly sincethe last time the engine was run (see Fine Tuning theCarburetor on page 36). Turn the high-speed needle out(rich/counterclockwise) 1/4 turn, hold the throttle trigger atabout 1/2 throttle and try again to start the engine. Oncestarted, retune the engine for performance (see page 35).The engine could be worn. If the fit between the piston andsleeve is loose, compression is reduced and the engine will bedifficult to start when it is warm, and may tend to stall whenrunning and when the throttle is closed suddenly to idle.Engine life depends on many factors including fuel type, airfilter maintenance, needle settings, and how the engine wasused. For example, if the engine was allowed to ingest dirtfrom lack of air filter maintenance or running through water,then the internal engine components could wear outextremely fast.▼ ▼ ▼ ▼Troubleshooting Your T-MaxxEngine performance sluggish:Engine performance depends mostly on the fuel mixturesettings and how they compensate for the currentatmospheric conditions. Before you suspect other failures withthe engine, richen the high-speed needle at least 1/4 turn andthen retune the engine for performance (see page 35).If the fuel mixture seems to be set correctly, make sure thefuel is fresh. If the fuel is old, or was left uncapped for a longperiod, then some of the important fuel components couldhave evaporated. Try new, fresh, Traxxas Top FuelTry a new Traxxas 3231 glow plug. Sometimes a glow plugwill work well enough to start the engine but not be able todeliver the engine’s full performance potential.Check to make sure there is no binding in the driveline thatwould cause excessive loads on the engine.▼ ▼ ▼ ▼ ▼ ▼Engine extremely sluggish, hard to start, and will not idleduring tank 1 of the break in:It is possible that the factory adjusted break-in settings onyour carburetor are too rich for your geographic location,atmospheric conditions, or fuel brand. Extremes intemperature, humidity, barometric pressure, and altitude can’talways be accounted for with a single high-speed needlesetting.The symptoms described above can occur when theair density is very low such as in high mountainous elevations,and extremely cold temperatures. Under these conditions,lean the fuel mixture slightly, 1/8 turn, to see if there is anyimprovement in starting and idling. Only lean the fuel mixturejust until the engine will run and idle reliably and thenproceed with the break in.The contents of different brands of fuel (other than TraxxasTop Fuel) in combination with extreme atmosphericconditions can also make the factory preset break-in settingstoo rich and cause the symptoms described above. Again, tryleaning the fuel mixture slightly, 1/8 turn, to see if there is anyimprovement in starting and idling.Clearing a Flooded Engine:If the engine is primed for toolong during startup, then it canbecome flooded with fuel.When the engine is flooded itwill no longer turn due toexcess fuel in the combustionchamber preventing upwardmovement of the piston. Usethe following procedure toclear a flooded engine.1. Remove the blue glowplug wire.2. Remove the glow plug andgasket with the glow plugwrench supplied with yourmodel. A 5/16 nut driverwill also work.3. Turn the model upsidedown and plug in theEZ-Start controller.4. Push the EZ-Start buttonfor several seconds to clearthe engine of excess fuel5. Turn the model over andreinstall the glow plug andgasket.6. Reconnect the blue glowplug wire to the glow plug.7. Reconnect the EZ-Startcontroller8. Do not prime the engine.Pull the throttle to 1/2throttle and push the EZ-Start button. The engineshould start immediately.43

Maintaining and Storing Your T-MaxxIf the engine isworn or damagedenough to requirereplacing the piston,sleeve, or connecting rod,consider exchanging yourold engine for a brand newengine under the terms ofthe Traxxas Lifetime EngineReplacement Plan (ERP). Itcould save you time andeffort. Details are in yourmodel’s documentationpackage.The TRX 2.5 isdesigned to be easyto rebuild. Criticalengine components suchas the crankcase,crankshaft, and enginebearings are made toextremely high qualitystandards and shouldunder normalcircumstances outlastmultiple sets of pistons,sleeves, connecting rods,and wrist pins(reciprocating assemblies).It could be moreeconomical for you tocontinue to use your goodbearings and crankshafts,and simply replace thereciprocating assembly asneeded. Engine assembly isnot difficult and replacingthe reciprocating assemblydoes not require anyspecial tools or skills.44Your T-Maxx requires timely maintenance in order to stay in toprunning condition. Neglecting the maintenance could allow dirt,deposits, and moisture to build up inside the engine leading tointernal engine failure. The following procedures should betaken very seriously.After each hour of running:Clean and re-oil the air filter.The instructions for thisprocedure are on page 27. We cannot stress enough thevalue of cleaning your air filter at the scheduled intervals.Do not neglect your air filter maintenance!▼ ▼ ▼ ▼ ▼ ▼Clean the outside of the engine of accumulated dirt, oil, andgrime. Accumulated grime will decrease the engine’s ability tocool itself.After each running session:Perform after-run maintenance on the engine.This clears theengine of destructive moisture and other corrosive deposits.This is extremely important for the life of the engine. Seepage 45 for after-run maintenance procedures.Inspect the vehicle for obvious damage or wear. Look for:1. Loose or missing screws2. Cracked, bent, or damaged parts3. Cut or loose wiring4. Cut or kinked fuel lines5. Signs of fuel leakageInspect the gears for wear,broken teeth, or debrislodged between the teeth.Other periodic maintenance:Slipper clutch pegs (frictionmaterial): The slipper clutchpegs will wear over time andrequire replacement.The lifeof the pegs depends on how the slipper clutch was adjustedand how the T-Maxx was used. If the slipper will not tighten oryou are seeing signs of wear on the face of the gear, then thepegs should be replaced.▼ ▼ ▼Piston/sleeve: The life of the piston andsleeve will vary greatly with how theengine was used and maintained.Thepiston and sleeve should be replacedwhen they no longer seal effectively(loss of compression). Symptoms includethe engine being difficult to start whenwarm, stalling when warm, and stallingwhen throttle is suddenly closed to idle.Replace the wrist pin and G-clipwhenever the piston and sleeve arereplaced.Connecting rod: The connecting rodshould be replaced when the piston andsleeve are replaced or after three gallonsof fuel, whichever comes first. Alsoreplace the piston wrist pin and G-clipwhenever the connecting rod is replaced. As with otherinternal engine components, connecting rod life dependsengine’s usage and the quality and frequency of theengine maintenance.EZ-Start: The cush drive elements in the EZ-Start driveunit should be inspected after 3-gallons of fuel. If the cushdrive elements appear deformed or hardened they shouldbe replaced. Inspect the EZ-Start gears for any signs ofwear. Damaged gears should be replaced. Coat the gearswith a thin layer of white lithium grease.

After-run ProcedureYou must perform after-run maintenance on your Traxxasengine whenever the model will be stored for longer than a fewhours. Taking the time to prepare your engine for storage willreward you with longer engine life, easier starting, and betterperformance.When a nitro engine is shut off, some excess unburned fuelremains in the engine. The methanol in model engine fuel ishygroscopic, which means it easily attracts and absorbsmoisture. This moisture can cause rust and corrosion on thesteel engine parts (crankshaft, bearings, wrist pin and startershaft) if the fuel is not removed from the engine. There are afterrun oil products available from your hobby dealer or you canuse WD-40 ,a common household lubricant. To ensure your TRX2.5 engine is protected from internal corrosion, use thefollowing procedure:1. Whenever possible, shut off the engine by pinching the fuelline closed. This allows most of the excess fuel to beconsumed by the engine. Be sure the throttle is in the idleposition. You may have to pinch the fuel line closed forseveral seconds before the engine stops.2. Completely empty the fuel tank. Use your fuel-dispensingbottle to suck out the old fuel. Do not mix the old fuel withyour fresh fuel supply. If you leave fuel in the tank,transporting or handling your T-Maxx may cause fuel to runinto the engine.3. With the fuel tank empty and the throttle at the idleposition, try to start the engine. The engine will most likelystart and run for a few seconds as it uses up any fuelremaining in the engine and fuel lines.4. Once the engine stops, clean the outside of the engine withcompressed air or spray motor cleaner. Once the engine isclean and dry, remove the glow plug power wire, glow plug,and air filter.Maintaining and Storing Your T-Maxx5. Open the throttle fully and spray a one-second burst ofWD-40 into the carburetor and into the glow plug hole(Caution! Wear safety glasses to prevent spray from gettinginto your eyes).6. Place a rag or paper towel over the engine to catch anyWD-40 that may come out the carburetor or glow plug hole.7. Connect the EZ-Start controller to the model and spin theengine for 10 seconds.8. Remove the rag or paper towel and repeat steps 5–7 twomore times.9. Clean and re-oil the air filter so it will be ready for use nexttime. See page 27 for air filter maintenance instructions.10. Replace the glow plug, reconnect the glow plug power wire,and reinstall the air filter.Denatured alcohol(available fromhome centers andpaint supply stores) in aspray bottle is an extremelyeffective cleaner. Be sure towear safety glasses andgloves when working withdenatured alcohol.Fun fact: WD-40 stands for “waterdisplacementattempt #40.” The WD-40 product used today was thesuccessful 40th attempt atcreating a water-displacinglubricant. WD-40 was thelab test label.Be sure to followproper maintenanceand storageprocedures to avoiddamage to your engine andother components of yourT-Maxx.Don’t put the fuelfrom your tank backinto your fuel jug.Dispose of it properly,following city or countyregulations.Always wear eyeprotection whenusing compressedair or spray cleaners andlubricants.45

Index46ABC 23After-run maintenance 21, 44, 45After-run procedure 45Air density 28, 35Air Filter 7, 22, 23, 27, 35, 44, 45Cleaning 21, 27foam 23maintenance 43oil 6, 27Air Intake 22Air temperature 36, 43Air/fuel mixture 28Air/fuel ratio 28, 29, 32Airflow 36Ambient temperature 36Antenna (receiver) 11, 15, 42tip 15tube 15wire 15Antenna (transmitter) 11, 15, 42Antenna Mount 7Atmospheric conditions 28, 36, 43Axle pins 9Barometric pressure 35, 43Baseline setting 35Batteries 6, 12, 13, 14, 42charging 30receiver 13, 14rechargeable 13, 14transmitter 13Batteries, Ni-MH (nickel-metalhydride) 13Batteries, NiCad (nickel-cadmium)6, 12, 13, 30Battery box 7Battery compartment (Transmitter)11, 13Battery holder 11, 14Bearings 45Big Block .15 23Binding 43Body mount 7Brake 19, 37Bulkhead 7Bumper 7Bumper mount 7CA glue 9Camber 39Carb, see also Carburetor 23Carburetor 22, 23, 28, 43adjustments 28barrel 23fine-tuning 35slide 25venturi 28Caster 40Channel 11, 12, 17, 18Channel number 12Charger 6, 30peak-detecting 30timed 30Chassis 7Clean-out 23Cleaning 44Clearing your frequency 12Clutch bell 22Clutch drum 38Combustion 28Combustion chamber 23Compression 24, 43, 44Connecting rod 23, 44Cooling fins 23Crankcase 22, 23Crankshaft 22, 23, 45Crashing 37Cross-brace 7Crystal 12, 18Access Plug 7Curbs 37Customer service 4, 42Cylinder sealing 32Decals 10Differential 7Drivetrain friction 37Driving Tips 37Dyno 23E-mail 4Engagement pawls 42Engine, TRX 2.5 7, 21, 22, 26"cutting out" 34break-in 21, 23, 32driving procedure 33cooling 36, 37, 44damage 27detonation 34failure 27, 44flooding 31, 42, 43hesitation 34idle 37life 43, 44maintenance 44mount 22overheating 34performance 29priming 25, 32, 43revving 42shut off 45sluggish acceleration 34stalling 25, 32, 34, 43, 44temperature 34, 36terms 23tuning 28, 34by temperature 36Exhaust 5, 22Exhaust fumes 32EZ-Start 6, 23, 24, 30, 42“glow plug” LED 30, 31, 42, 43“motor” LED 30, 31, 42, 43battery 30, 42controller 22, 31, 42, 43, 45cush drive 30drive unit 22motor 7, 22, 31, 42plug 7, 22Protection Mode 31, 42Smart Start 30, 31Fit 23Flag color 12Flame-out 24Flipping 37Flooding, see Engine; floodingFlywheel 22, 42Forward and Reverse Operation 37Frequency band 12, 15Fuel 5, 6, 24, 26, 43, 45break-in fuel 32fuel dispensing bottle 6, 26Traxxas Top Fueler 26Traxxas Top Fuel 24, 26, 43unburned 45Fuel flow 28Fuel intake 22Fuel line (fuel tubing) 7, 22, 24, 43Fuel mixture adjustment 35high-speed fuel mixture 34low-speed mixture 35Fuel mixture, see also air/fuelmixture 24, 34, 35, 43Fuel tank 7, 22, 26, 45emptying 45filling 26fuel level 32tank lid 7, 26tank seal 26Glow plug 24, 30, 31, 32, 34, 43driver 24fouled 32igniter 30power wire 22,43,45Ground wire 22Half shaft 7Head (cylinder head) 22, 23Head Protector 22Header 7, 24Hex hubs 9Humidity 35Idle adjustment screw 35Idle speed 17, 24, 29, 32, 33, 34, 35,42Idle Speed Adjustment 29, 33, 35Idle Speed Screw 22, 24, 29Jump 37

IndexJumping 37Lean 24, 29leaning the mixture 24maximum safe lean setting 34-35,36Lubrication 29Maintenance 44Maintenance schedule 21Methanol 45Mixture needles 34high-speed needle 22, 24, 28, 35, 43low-speed needle 22, 24, 28, 35Moisture 44, 45Needle seat 28Needle settings 43Needle valve 24Negative wire 22Neutral (center) point 17Neutral position 12Nitro 24content 24, 26percentage 26compensating for 35Nitromethane, see also Nitro 24O-ring 24Oil 6after-run 6, 45filter 6, 27WD-40 6, 45Oil Dampers, see ShocksOn/Off switch 7, 11, 14, 18, 42Over-revving 37Peak Detection, see ChargerPinch test 35Pipe (tuned) 7, 22, 24, 25Pipe hanger 7Piston 24, 32wrist pin 44, 45Piston and Sleeve 43, 44Pivot Balls 39Port 24Positive Wire 22Power Switch 11Pressure Line 7, 22Primary gear shaft 38Priming, see Engine; primingProGraphix 10Punch 25Quick Start 8, 9, 10, 13, 14, 15, 18,19, 20, 26, 30, 31, 32, 34, 37, 44Radio interference 5, 20Radio System 11, 12, 19, 42adjustments 17controls 16range-testing 20rules 18terminology 12terms 12Range 14, 15, 18, 20, 42short 42Receiver 11, 12, 42cover (box) 7, 15, 42Required equipment 6Reverse 19, 37, 42Rich 25, 29Ride height 41Rollovers 37RPM 25limits 37Safety 5Servo reversing switches 11, 17Servos 7, 11, 12reversing 11, 17shifting 7, 11, 19steering 7, 11, 17, 19throttle/brake 7, 11, 17, 19Shift button 11, 19, 37, 42Shift point 38Shift Rod 7, 19Shifting 34, 35, 37, 42Shipping 4Shock Mounting Positions 40Lower 40Upper 41Shock Tower 7Shocks 7Fine Tuning 39Shuddering 42Skid Plate 7Sleeve 25, 32Slipper Clutch 7, 38, 44adjusting 38pegs 44Smoke 34Spring progression 40, 41Spring rate 40, 41Spur Gear 7, 38Stalling, see Engine; stallingStarter shaft 45Starting, see Engine; startingSteering mechanism 19Steering Trim, Electronic 11, 12, 17,19Steering Wheel 11, 19Storage 45Supplies 6Support 4, 42Suspension 39adjusting 39, 40, 41Suspension Arms 7Tank 1 33Tank 2 33Tank 3 33Tank 4 33Tank 5 33Tank 6 33Temperature, see Engine;temperatureTemperature gauge 36digital temperature gauge 36infrared temperature probe 36Throttle Arm 22Throttle Neutral Adjustment 11, 17Throttle response 35Throttle slide 35Throttle Trigger 11, 17, 19Throttle Trim, Electronic 11, 12, 17,19, 35Toe-in 39Tools 6TQ-3, see also Radio System 11Transmission 7, 42housing 38two-speed 38Transmitter 12, 18, 42indicator light 19power indicator 11, 13Traxxas Lifetime EngineReplacement Plan 44Trim, see also Throttle Trim andSteering Trim 12Troubleshooting 42Turnbuckle 7Turns 37Two Speed Access Plug 7, 38Water 43Wear-in 25Weather conditions 35Wheelies 34, 37Wheels 9Wiring diagram 11WOT 25, 28X-tal see also Crystal 12Zero-scrub-radius 1947

Traxxas Corporation, 1100 Klein Road, Plano, Texas 75074, Phone: 972-265-8000, Toll-free 1-888-TRAXXASTraxxas U.K., P.O. Box 1128, Winterbourne, Bristol BS17-2SH, England, Phone: 44-117-956-1002Internet: www.Traxxas.com, www.T-Maxx.com