oil pump prime

[sccowboy]

Are you sure the oil pump gear is properly engaged on the counter balance shaft? I can't think of a single reason why it won't maintain prime unless wither the inlet port is stopped up or the pump isn't sealed properly as in it sucking air from somewhere. New O rings on both the pump cover and the filter?

[Coryhayess]

Update: I just started up the cart without priming the oil pump and I immediately build pressure. It seems that when the engine reaches a warm temp the oil pressure falls. I will confirm again tomorrow. I am running just a regular 10w30. Any thoughts of maybe a thicker oil?

[sccowboy]

Thats whats called for. I would run it and keep and eye on it if you are confident that you followed all the steps to rebuild according to the book. When I did mine I never worried about the pressure switch since it wasn't connected to anything anyway. Its been running like a top.

[raydhd]

I see fresh rebuild and wonder are your bearing and pump clearances right?

[Coryhayess]

I'm not sure what else I can check as far as clearances with the pump go. I've replaced both gears and the cover and all new O rings all the way around. Again this evening fires right up with great oil pressure. But a few minutes into it pressure falls and eventually is nothing. Not sure how the engine being warm could have an effect on this.

[roady89]

Isn't there a relief spring in there....look at item 93. Could be a sacked out spring affected by heat. Or possibly warping in the case when heated.

[sccowboy]

If you refer to the manual, you will find the measurements and tolerances for the engine. There is a spacer that goes on the end of the balancer shaft. The manual has a formula for measuring to determine the correct spacer for both the crank and balance shaft. I believe that this spacer is for end play of the shaft and should not affect the pump since the pump is on the outside of the case cover and the spacer goes on the inside. If the oil pickup tube which runs from the bottom of the crank case into the cover and up to the pump is clear, and the pump rotor is turning within the outer rotor, then there certainly has to be pressure. With that being said, when you rebuilt the engine, did you vat the block and head etc.? I took mine to a large parts washer and thoroughly flushed each piece, running a brush and wire through all the little passageways to ensure that no gunk or trash was left inside. It took a while but I didn't want to take any chances on any metal frags being left behind. I broke a con rod and there was a ton of trash inside when I started. Just a thought.

[sccowboy]

Roady, I asked him about the check valve and he said it was good, but I agree it could be failing.

[Coryhayess]

I have cleaned all the ports in the head, I will order a new relief valve and try that. I've tried everything else. Thanks guys I will update you with what I find with that

[Coryhayess]

Ok I'm stumped. Tried a new pressure relief spring and still no different. Good Oil pressure until the engine reaches temp the it falls to zero within a min.