Oil Strainer Tip

[Fox]

On the 4T engines there's an oil strainer screen located on the bottom of the engine under a plug. It's there to catch any large debris before it gets to the oil pump. If it does catch anything, it will get caught on the outside of the screen not on the inside. I found that out when rebuilding an engine with a bad lower con rod bearing.




Also, you don't need to drain the oil from the strainer plug. It has an O-ring on it that will wear out from excessive removal of the plug. #10 below.



I never remove the strainer on a scoot unless I suspect that there may be some engine damage. I drain the oil with the drain plug on the lower left side of the engine case.

[speedy1125]

Good point on the captured material being on the outside rather than inside. I am thinking the only purpose of the oil pump on the 4 strokes is to push oil through this strainer, since there are no passages up to the head.

[Fox]

Actually there is oil pumped through to the head that lubricates the rocker assy. The shafts the rocker arms pivot on are hollow and drilled full of holes. That's the whole purpose of the pump. The lower connecting rod bearing and the Gudgeon (piston) pin are lubed by oil splash.