Topic: Oil pump priming CB750

[Seamus]

Too late now, but when I was trying to get oil pressure from a rebuilt engine, I pulled off the pan and removed the oil stop valve for a few seconds. (This is there to prevent oil from the tank flowing into the sump, so I guess it will also hold an air lock)
As soon as oill started to flow, I put it back. Replaced the pan and instant oil pressure.

Cheers

Seamus

[Turbogrimace]

Neat trick Seamus.  But my oil stopper already leaked, so there was plenty of oil in the pan when I was working on it.

[Seamus]

If the stopper was leaking slowley, there would be oil in the pan, but that is not important. The air lock is in the pump and the leak through the stopper will not let that air out. If you actually remove the stopper valve and open up the whole pipe, then the air can move .

Hope this makes sense

Cheers

Seamus

[Henning]

Problem solved, but I'll chip in anyway for future reference. After having had the motor of my 750 K1 out to do the head gasket, I stored it upside down on the workshop floor for a few days to clean off 35 year old gunk. As guru HondaMan stated, this will drain oil out of the oil pump, and true enough, it kept on leaking oil out of every available orifice, long after I thought it must be empty.

After reinstalling the motor, I couldn't get oil pressure, despite continuous cranking and the onset of mild panic. Then I figured it might have to with oil having drained out of the pump and an air block. So I took it off the mainstand - which you would use when removing/replacing the engine - and put it on the sidestand. Then after a short amout of cranking, Lord Be Praised, I got oil pressure. I guess the air bubble moved enough so that the pump could do its thing. If the sidestand isn't enough, maybe you could lie the bike further down on its side to move that bubble - easier than removing the pan and pump.

- Henning

[HondaMan]

Problem solved, but I'll chip in anyway for future reference. After having had the motor of my 750 K1 out to do the head gasket, I stored it upside down on the workshop floor for a few days to clean off 35 year old gunk. As guru HondaMan stated, this will drain oil out of the oil pump, and true enough, it kept on leaking oil out of every available orifice, long after I thought it must be empty.

After reinstalling the motor, I couldn't get oil pressure, despite continuous cranking and the onset of mild panic. Then I figured it might have to with oil having drained out of the pump and an air block. So I took it off the mainstand - which you would use when removing/replacing the engine - and put it on the sidestand. Then after a short amout of cranking, Lord Be Praised, I got oil pressure. I guess the air bubble moved enough so that the pump could do its thing. If the sidestand isn't enough, maybe you could lie the bike further down on its side to move that bubble - easier than removing the pan and pump.

- Henning

Hey, thanks! I'll try that next time, before pulling the pan and pump back out...

[JLeather]

just throwin' it out there, but Turbo's bike is a Santee chopper.  Pretty sure there's no center-stand, only a sidestand.

[Turbogrimace]

Yeah... No center stand.   

But to add to what's already been said, I tried to figure out the best way to get the air out of the pump and the more you lean it to the left (towards the side stand), the more the air comes out faster.  So in all, I'd say you could simply lean the bike over really far and it will release the air bubble.  I did this a few times with the pump in my hands while it was soaking in a bucket of oil.  Same thing should be going on in the engine, so just leave it in the bike and tilt it over.   Put some straps on the bars and support it from some rafters and kick away.  Or have one of your minions hold it over for you.

Good advice in this thread.  I'll bet leaning it over would have done enough to let the bubble out now.  It was good practice to take the pump out 5 times though.  I can swap the pump in 5 minutes now hahaha.