Topic: 750k - How to tell if oil pump is failing?

[Benjamin]

Hi all, I have a '76 CB 750 with a lot of top-end noise. Almost sounds like a scraping sound. It's my imagination that not enough oil is reaching the top end. Is it possible for oil pumps to weaken over time, or do they simply fail?

Or might it be a simple valve adjustment issue?

All opinions welcome. Thanks!

[WiredForStereo]

The best way would be an oil pressure guage, or you could take apart the oil pump and check the tolerances as the Clymers manual suggests, or keep an eye on the oil pressure light, though that wouldn't help you if there is plug after the oil pressure sender.  It would probably be a good idea to look in the top to make sure nothing is going on.  Adjust the valves, use better oil, and keep a close ear on strange sounds.

[toycollector10]

I'm not sure about your model but look into your oil tank with the motor running
and you will see, or should see the oil returning to the tank. On my K0 the flow exited
the return pipe and stood up for about two inches before gravity took over..

[Clyde]

A pressure test would be worthwhile, but may not show up the problem.
The usual problem is that there has been insufficient oil getting to the cam bearings and they run dry. There are two small orifices that feed them and if the oil/filter is neglected then these block.
The best test is to remove each exhaust valve cover one at a time. Start the engine and if all is well, you will see a spray of oil coming out over the rocker gear. Have a rag ready as it is a bit messy, but it is a positive test that oil is getting to the end of the line.
You may have to rev the engine slightly to see the oil spray.
There are four small holes which spray the oil hence the need to check all four valve covers.

I guess you have checked the valve clearances, cam chain tension etc?

Good Luck
Clyde