4-CYCLE OVERHEAD VALVE ENGINES - Small Engine Discount
4-CYCLE OVERHEAD VALVE ENGINES - Small Engine Discount
4-CYCLE OVERHEAD VALVE ENGINES - Small Engine Discount
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LUBRICATION SYSTEMS<br />
The lubrication system used with all Tecumseh<br />
horizontal crankshaft engines covered in this manual<br />
utilize a splash type system. An oil dipper on the<br />
connecting rod splashes oil in the crankcase to<br />
lubricate all internal moving parts. The oil dipper is<br />
either bolted on or may be cast on to the cap with one<br />
of the rod bolts (diag. 6).<br />
All vertical shaft engines use a positive displacement<br />
plunger oil pump or a rotary oil pump. Oil is pumped<br />
from the bottom of the crankcase, up through the<br />
camshaft and over to the top main bearing. Oil under<br />
pressure lubricates the top crankshaft main bearing<br />
and camshaft upper bearing (diag. 7). A crankshaft<br />
drilling also provides oil to the crankpin journal on<br />
engine models OHV 13.5 -16.5.<br />
On all Tecumseh vertical shaft 4-cycle engines, the<br />
oil is sprayed out under pressure through a small hole<br />
between the top camshaft and crankshaft bearing to<br />
lubricate the piston, connecting rod, and other internal<br />
parts (diag. 5).<br />
The plunger style oil pump is located on an eccentric<br />
on the camshaft. As the camshaft rotates, the<br />
eccentric moves the barrel back and forth on the<br />
plunger forcing oil through the hole in the center of<br />
the camshaft. The ball on the end of the plunger is<br />
anchored in a recess in the cylinder flange (diag. 8).<br />
SPRAY<br />
MIST HOLE<br />
CRANKCASE<br />
PASSAGE<br />
PLUG<br />
CAMSHAFT<br />
DRILLED<br />
CAMSHAFT<br />
PASSAGE<br />
DIPPER 6<br />
MAIN BEARING<br />
OIL GROOVE<br />
BARREL TYPE<br />
LUBRICATION<br />
PUMP<br />
CRANKSHAFT<br />
OIL PASSAGE<br />
ASSEMBLE PUMP HOUSING<br />
WITH INSIDE CHAMFER<br />
TOWARD CAMSHAFT GEAR<br />
7<br />
The rotary pump is driven by the camshaft. It uses a<br />
lobed gear in a rotating ring to provide positive oil<br />
displacement (diag. 9).<br />
SPRAY<br />
MIST HOLE<br />
FLAT<br />
8<br />
OIL DRAIN<br />
HOLE<br />
COUNTERBALANCE SYSTEMS<br />
Some Tecumseh engines may be equipped with an<br />
Ultra-Balance ® counterbalance system. This system<br />
uses a single weighted shaft that is driven off the<br />
crankshaft. This shaft's function is to counteract the<br />
imbalance caused by the counterweights on the<br />
crankshaft (diag. 10).<br />
A dual shaft counterbalance is also used on some<br />
engine models. A gear on the crankshaft drives the<br />
counterbalance with the thicker gear, which in turn<br />
drives the second counter balance shaft. For timing<br />
of either counterbalance system, see " <strong>Engine</strong><br />
Assembly Procedure " in the Service section of this<br />
CAMSHAFT<br />
chapter.<br />
Not For Resale<br />
5<br />
NOTE: INSTALL OIL PUMP AFTER THE SUMP IS ON<br />
DRIVE<br />
GEAR<br />
www.<strong>Small</strong><strong>Engine</strong><strong>Discount</strong>.com<br />
COUNTER-<br />
BALANCE<br />
SHAFT<br />
GOVERNOR<br />
FLANGE<br />
9<br />
10<br />
59