Plunger Type; Oil Pump Operating Principle - Honda Motorcycle Service Manual

LUBRICATION
PLUNGER TYPE
Virtually all non premix lubricated 2-stroke engines are equip-
ped with a plunger-type oil pump.
Some plunger pumps are driven by crankshaft via the oil pump
gear shaft, and others are directly driven by crankshaft.
The oil pump cam is depressed under a spring. Turning the cam
causes the plunger to reciprocate so that the pumping move-
ment is repeated. The amount of lubricant is controlled propor-
tionally with the cam rotation.
The pump is designed to control the amount of lubricant
discharged per crankshaft rotation by varying the plunger
stroke through the operation of the cam interlocked with the
carburetor throttle.
The combined function of these t w o mechanisms allows the
proper flow of lubricant depending on load conditions and
engine rpm.
GEAR
Oil Pump Operating Principle
VALVE
PLUNGER : : ? O N
/
I
I
(Suction process) (Discharge process1
DISCHARGE CAM
PORl
(11 As the valve descends, it blocks the outlet passage while gradually opening the inlet passage.
(2) Here at the "bottom dead center" position, the outlet passage is completely closed while the inlet passage is completely
opened - allowing free flow of oil into the pump chamber.
(31
With the oil chamber filled, the valve ascends
-
closing t h e inlet passage.
(4) The valve ascends further, allowing free flow of oil through the outlet passage.
( 5 ) The plunger also ascends, compressing the oil inside the pump chamber and pumping oil out through the outlet passage.
towards the intake pipe via the outlet line.
4-8
Date of Issue: Sep.. 1988
O
HONDA MOTOR CO., LTD.