SOHC.co.uk Forums > CB750

oil pump rebuild

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adriangsmith:
Are the jets in the head unblocked ?Yes. this is what caused me to strip it down in  the first place as one was blocked with a grain of sand and wrecked the cam and carrier.
The oil travels up the head studs, are these oil ways clear ? Clean as a die. made sure of that one
Is oil getting to the oil filter bolt ? No oil what so ever :-(
Do all the main oil ways have there caps on tight and is the oil pressure switch nice and tight ?yes
Did you put a new O ring in were the crank cases fit together and the O ring fits round a dowel ? Yes

No oil at all even with the filter removed.
Pump does not want to pick up.
Main gallery totally dry.
Going for a final strip degrease and full cleanup of the pump again tomorrow.
Found some useful information pages 300 - 304 of Ash's mega manual.

I get the feeling the pump is the issue as i cant seem to get it to prime properly even with vaseline.
Anyone got a referb'd one they want to do an exchange on???

Trigger:
If it is not picking up, is the stopper valve working ?
Are the oil lines clear ?
Seems very strange to me because the oil from the tank has enough weight behind it.

K2-K6:
You could, with both the pump and filter removed, check the path between the two to make sure it's not obstructed.

The oil pump should at least pass oil though it if you fill the feed side and turn the drive wheel by hand.

Most pumps even if really old and baggy will pump oil,  maybe not reach the correct pressure, but you'll get it to go through them. There's something odd we're not getting on this one.

adriangsmith:
Hi All,
Pump all ultrasonically cleaned and valve section reassembled.
Both valves slide freely with no undue play.
Double checked all rotor clearances and they are well within their servicable limits. In fact very little wear seen at all.
The only part I never replaced was the shaft oil seal.
Are these still available? if so does anyone have a part number or dimensions?
I'm going to reassemble this with only a film of oil in the rotor half, that vaseline was a complete pain to remove!
Will hold off rebuilding the rotor section until i can find out if i can obtain the shaft oil seal.

I also blew compressed air through the oil filter inlet and outlets and both were clear.

MrDavo:
It's a great little pump, but a tw*t to start.

Don't put the oil pump back until you get it so as you pack Vaseline (petroleum jelly - same stuff, no brand name) in to the feed port, a column of the stuff rises from the port to the oil filter as you turn the pump. You'll soon work out which is the correct way to turn it. Although I also filled the (larger) return chamber you can't get the stuff into the port the same way because of the screen, concentrate on the feed.

To help, I took the stopper valve out again, just undo the two screws on the end cap. I packed the Vaseline into the feed port until it was coming solidly out of the engine side, then I put the valve back in. The pressure of the stuff then pushed the piston back enough as you turn the pump wheel so a solid column of Vaseline rose from the port on the engine side. I keep packing the stuff into the feed port, where the oil feed attaches, as I didn't want another air lock.

Now you can put the pump back, don't turn the engine at all until you at least have the inlet line on and a decent head of oil in the tank. If you were to turn it over before, as there is no new Vaseline going in, you will create an air lock again, go back to the start. Once you have an oil supply, and start turning the pump the oil will replace the Vaseline as it goes through the pump.

Maybe you checked at this point (before providing an oil feed) that you had drive to the pump and that it turned ok as you turned the engine over (have you checked?) this would be enough to cause an air lock and 'unprime' the pump.

I assume the shaft seal between the two chambers is there and ok. Mine was as hard as a rock and a sod to get out to change. I just saw the reply you made while I was typing, Trigger can source these.

However if you are 'doing it wrong' your results won't be any different with another pump, I was tempted but it would have been a waste of time and money. Even a shot pump should work a bit, otherwise the oil light would have been on hard when the engine last ran, with accompanying mayhem  to all the bearings.

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