Topic: CB750 k2 Oil Pressure issues

[rhos1355]

Hi guys,
Have some oil pressure issues on the bike.
I recently drained all the oil from both the tank as well as the engine to fit new hoses and a return valve kit in the oil pump assembly.
I now have the situation where the oil light is on all the time. It almost goes out when I rev the engine up to 2000rpm but starts to flicker and then comes on permanently after that.
I always had oil issues before replacing the hoses (one was badly kinked in the middle) and the non return valve would drain all the oil into the engine. But I've never suspected the pump to be at fault.
How do I assume this? Well I loosened the return hose to the tank and turned the engine, and a jet of oil shot out of the open end of the hose.
I don't think the oil pressure switch or sender is at fault either as I have fitted an oil gauge and even that records very low oil pressure.
would it be a case of replacing the whole pump just to see if that's the culprit or,  check the clearances etc, which to a non technical guy like me will not tell me anything.
Is there a way to check the the pump when it's out of the engine?
Or could it be just a simple case of letting the engine idle for about 15 minutes to let the pump prime itself enough to build pressure.
Oh yea, I have also opened one of those valve ports on the valve cover, and whilst the parts inside seem well oiled it doesn't spurt out like as described by other members here.

Cheers

[enwri]

Did you check the O rings and sleeves between the pump and case as well?

[mcpuffett]

Hi Rhos did you prime the pump before you installed it ? , I had the same thing happen to me after a rebuild I took the sump off and loosened something on the oil pump and primed it and it sorted it out  cheers Mick.

[rhos1355]

by priming the pump, I assume you mean make sure it is full of oil before mounting it to the engine casing?
is there a tried and trusted method of doing this?
I suppose this would be a good time to check those 'O' rings and 'sleeves'  (by sleeves do you mean the connecting spigot??)

many thanks

[70CB750]

You submerged the oil pump in a container of oil and keep spinning the gear till no bubbles come out anymore.  Messy job, but important.

[rhos1355]

CHEERS, MATE

[rhos1355]

ok, here's an update.
removed oil pump and primed it as explained by 70cb750. checked all 'o' rings & made sure the 'faces' between the pump and the engine casing married up tightly.
replenished the oil (3.5 litres) and fired the bike up. after a few seconds the oil light went out, and between 1000 and 2000rpm stayed out (i didn't want to go too high on the revs) then suddenly the revs dropped to idle and the light came back on again. And stayed on. so I shut the bike down, and after a while, checked the level in the tank. It was way over the 'chequered' range on the stick.
looks like I'll either be trying buy another pump off e-bay, or another dismantling job for the next week.

[mcpuffett]

Do you have another oil pressure switch you could try ? just to rule it out ? cheers Mick.

[rhos1355]

I thought about this too, but it's brand new (well it WAS 5 years ago when we did the engine and the bike hasn't run for more than 20 minutes since then) and also, I've rigged up a 'clock' pressure gauge and that too is registering almost zero pressure.
But I'll check David Silver and see if they have new ones in stock.

[enwri]

by priming the pump, I assume you mean make sure it is full of oil before mounting it to the engine casing?
is there a tried and trusted method of doing this?
I suppose this would be a good time to check those 'O' rings and 'sleeves'  (by sleeves do you mean the connecting spigot??)

many thanks

The No.9s in the diagram

[rhos1355]

ok, enwri, I now understand what you mean. We call them 'dowels' over here.
If i remember correctly, they were all in place with the associated 'o' rings attached.

thanks