SOHC.co.uk Forums > CB750

oil pump rebuild

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K2-K6:
Thinking about it a bit more laterally, filling the main gallery (the one behind the barrels with cap on clutch side) will only provide oil sooner to the head area once the pressure comes through. Don't think it will run back via the filter to the pump head.

I think it's the oil filter that will give an outgoing restriction to the pump regarding air lock, ish. So if you took off the oil filter and just keep slowly turning the engine with the kick start you may see oil come out of the filter feed. If that's successful, refit the filter and it should start to build pressure if the pump has filled.

MrDavo:
Been there done that, was driven to visit Boots for a tub of Vaseline after Trigger told me how many motors he has re-rebuilt after they were started with no oil pressure and posted a link to someone selling up in disgust as a result.

Take the pump apart and pack it full, I then packed it the ports until it emerged into the chamber. I then turned it a bit, packing Vaseline in as it rose from the outlet. Back in place, oil in, the red light went out after only a few kicks, much to my relief.

A bit more kicking and it was running out of the gallery. I'd packed both sides of the pump, I also noticed Vaseline floating in the oil tank, which could only have got there up the return pipe.

Trigger:
Boots for vaseline ? I always get the big budget tubs from the 99p shop

philward:
I have been following the various start up oil pressure threads and having had difficulty getting pressure on the last rebuild, am picking up tips for the next start up (some time off yet). I am obviously going the multi recommended vaseline route but am intrigued at what point do you change the oil tp get shut of the residual vaseline from the oil - we are all so particular about our oils/viscosity, given that vaseline isn't made to lubricate with the loads on a hot engine, won't there be bearing damage if you don't change the oil ASAP?
Over to you SOHC experts!

K2-K6:
As a proportion of the oil it's insignificant I feel.

Of far more concern for me in oil properties is the dilution caused by running on choke for any appreciable accumulated time for these engines. For any engine of this type I don't think it's good practice to start it and not let it warm up fully, for the bores, oil condition and any of the standard pipes really.
The incompletely burnt fuel and condensation containing acid byproducts of petrol combustion aren't good at all.

One of the biggest advances in petrol engines is to run them so lean when not under load nowadays that even the exhausts can last to 200,000miles or more. They just didn't do that on carbs.

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