4-CYCLE OVERHEAD VALVE ENGINES - Small Engine Discount

If further adjustment is required, the main adjustment should be made under a load condition.
If the engine stops or hesitates while engaging the load (lean), turn the main mixture adjusting screw out
(counterclockwise) 1/8 turn at a time, testing each setting with the equipment under load, until this condition is
corrected. A few Tecumseh carburetors were built as air adjust idle system. If you have one, the adjustments
are reversed out for lean in for richer.
If the engine smokes excessively (rich), turn the main adjusting screw in (clockwise) 1/8 turn at a time, testing
each setting with the equipment under load, until this condition is corrected.
After the main mixture screw is set, move the speed control to the IDLE or SLOW position. If the engine does
not idle smoothly, turn the idle mixture screw 1/8 turn either in (clockwise) or out (counterclockwise) until
engine idles smoothly.
Recheck the high and low R.P.M. setting and adjust as necessary.
CARBURETOR DISASSEMBLY PROCEDURE
NOTE : CARBURETORS THAT ARE EMISSION COMPLIANT (MANUFACTURING NUMBERS 5000 OR
GREATER) WITH FIXED IDLE OR MAIN JETS ARE TO BE REMOVED BY DEALERS ONLY FOR INSPECTION
AND CLEANING.
1. Note or mark the high and low mixture adjusting screws to aid in reassembly (if applicable). Remove
the high speed mixture screw, bowl nut, and float bowl. Remove the idle mixture screw assembly. On
Series 7 carburetors, release the wire retainer that retains the bowl and remove the bowl assembly. If
a screwdriver or similar tool is used to release the retainer, carefully move the retainer to prevent
bending of the wire.
2. Series 8 carburetors have a tamper resistant cap, over the fixed idle jet. (diag. 21). The cap is removed
by piercing it with an ice pick or similar instrument, then remove the jet for service, always replace the
cap.
3. Note the position of the spring clip on the inlet needle and float. Remove the float hinge pin with a
needlenose pliers. Some carburetors use a float dampening spring to aid the inlet valve to maintain a
steady position in rough service applications. Note the position of the hooks before removing the float
hinge pin (diag. 25). On Series 7 carburetors, grasp the crossbrace on the float with a needlenose
pliers and pull straight out to release the float hinge pin.
4. Remove the float, clip, and inlet needle.
5. Remove the inlet needle seat using a wire or a paper clip with a 3/32" (2.38 mm) hook end (Tecumseh
carburetors only, Walbro model LMK uses a non-serviceable seat). Push the hook through the hole in
the center of the seat and pull out to remove it.
6. On Series 7 only, remove the main nozzle tube, "O" ring, and spring located in the center leg of the
carburetor bowl. Remove the bowl drain screw and gasket. Remove the spring, metering jet, and "O"
ring.
7. Note or mark the action of the choke and throttle shutters and the hook points of the choke or throttle
return spring or seal retainer springs located on the top of the choke or throttle shaft.
NOTE: MARK THE EDGES OF THE THROTTLE AND CHOKE SHUTTERS PRIOR TO DISASSEMBLY.
THE SHUTTERS HAVE BEVELED EDGES AND MUST BE INSTALLED IN THE ORIGINAL POSITION.
Remove the throttle shutter, throttle shaft, choke shutter, springs and choke shaft by removing the
screw or screws that attach the throttle or choke shutter to the shaft inside the air horn. To remove the
choke shaft assembly on Series 7 or Walbro LMK carburetors, grasp the choke shutter with a pliers
and pull it through the slot in the choke shaft. Slide the choke shaft out of the carburetor body.
3/32"
(2.38 mm)
LONG END
OF CLIP
CLIP
OPEN END
OF CLIP
14
CHOKE
END
THROTTLE
END
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