Topic: No oil pressure 72 CB750

[treetrimmer]

Hi all,
Here's the story. I am reassembling my 72 CB750 after having the frame powdercoated. After reading the helpfull hints i decided to remove the oil pan and pump to make it easier to reinstall the motor. Well now that I have it 90% back together I fill up the oil tank and even after lots of kicking and cranking I have no oil pressure. This is with a gauge mounted in the usual place. Yes I did remember to reinstall the pump and pan with new seals and a gasket. Do I need to prime the pump or something? Lots of oil pressure prior to disassembly. pictures soon!

Thanks,
Jeff

[Bob Wessner]

I had occasion to remove my oil pump and I did prime it before reinstalling it. I don't know that you would get much noticeable pressure kicking it, but if you remove the spark plugs, just to take some of the load off, and crank with the starter, you should get the light to go out with the proper amount of oil and with the pump primed.

[kghost]

Yes prime the pump.

I pack mine full of lubriplate when I put them together and that picks up a prime.

Heres what you do.

Pull the spark plugs.

Pull the left gallery plug where the gauge is.

Put a bit of compressed air on the oil tank...I just cover the oil filler with my hand while applying a little compressed air under it.

Spin the engine till oil appears out the gally plug.

[Jonesy]

Another way is with the oil pan off and some oil in the tank, remove the pressure regulator valve and crank the engine until you see oil come out of the valve bore. Replace the cap and watch for oil filling the oil galleries when the engine is cranked. It was what I had to do after nothing else seemed to work...

[Clyde]

Your oil pump is probably full of air and will not prime.
Pour half a liter of oil down through any of the valve adjustment holes.
With the bike on the side stand undo the small oil gallery plug which is situated on the right hand side near the points cover (probably where your gauge is connected). Pour as much oil as you can until it can take no more.
Put the bike on the centre stand and you should have oil pressure when you start
Regds Clyde

[pddpimp]

Do what Clyde said. I just had this same problem last week, followed the process above, and had oil pressure within 15 sec.

[Edwin_SOHC]

Thanks guys, 10 years later and it still works ;-)
Wouldn't know how I could have solved without your all's help.
--Edwin

CB750K2 1972 (fully restored, compelted upong this forum thread)
CB750F1 1976 (next job: long & low, will get 836 and mechanical compressor)
CB750F1 1977 (immaculate - riding it for 30 yrs)
CB750F2 1978 (in parts)
CB750K7 1978 (in parts)

[flybox1]

Purdy!