my oil light keeps coming on on my '80 kz750 twin

zukdave wrote: Take your finger and dip it in the old oil and go out in the bright
sun light and look at it if theres gold or silver specks in it and you are
having keep rising the idle rpm to keep the oil light off and you said it runs real hot
you have a rod, main or cam bearing issue.
.

The 750 twins have no cam bearings, but I would definitely agree on rod/main beraing opinion.

JR wrote: Google "Biquetoast 750 twin"

Biquetoast used to be a member here and he has a lot of information on kz750twins.com

From a quick look at a pdf page from the 79 750 twin manual I think the oil pump access is via the oil pan

It is above the pan, pretty easy to remove.

Even with no cam bearings it could still be chewing up the bearing surface in the head
and that could be the silver flakes

so we dropped the pan and the pump screen had sludge. cleaned it out. the pan did have debris in it also. we went to a garage and talked to the shop owner about it. He thinks the flakes in the oil could be from the cam chain.

To me it seems highly unlikely that any metal has flaked off the cam chain, but that should be easy enough to check. Just pull the valve cover off and you can examine the chain. Ed

I doubt it's the cam chain. If the oil pan is off, I think you can look up and see the bottom of the chain where it goes around the crankshaft gear. See the picture below. The cam chain should be just above the pump.

Here's the manual for the oil pump. If you have the screen off you may want to spray some carb cleaner up and into it to clean out the debris.

so we had pulled the pan, cleaned the screen and the inside of the pan out. Replaced the gasket and let the oil cycle through and finally took it out and once again the light is coming on. is it possible that i am just not going fast enough to cool the oil since i am just learning on it? or is there a different issue possible?

FIRST: I would find somebody with an oil pressure gauge and measure it so you know what's going on. Metal shavings plus low pressure point to one thing: damaged bearings. Attached see the oil flow chart from the factory manual. Notice the flow goes through the filter and to the crankshaft (bearing) journals and then the (piston) connecting rod journals. If there is wear in those bearings, the physical spacing that the oil flows through increases and that means the pressure drops.

Is the pressure light coming on at idle only or all the time?

One thing you can try: put in 20-50 oil and see if it improves.

Like I said, I would get a pressure gauge and see what it is actually putting out. It could be wear in the oil pump but that's unusual. Mine had 80k miles at rebuild and the pump checked like new for wear.

No.
You have an issue. Before tearing down....
Is there any way to put an oil pressure gauge in the engine so as to eliminate the pressure switch, grounds and or wiring?

from previous:

The light comes on when its idling and then the idle has to be higher and higher to keep it from coming on.

If that's the case, it sounds like engine wear and very likely the bearings. You could see if 20-50W oil makes any significant change. I would still check pressure with a gauge.

The manual only gives a spec at 4000 RPM (see attached). I believe the warning light comes on if it drops below about 5 psi (?) ballpark.






I have read posts from other people with bikes that flashed the light at idle and they still rode them. Not sure how safe that is.

missionkz wrote: No.
You have an issue. Before tearing down....
Is there any way to put an oil pressure gauge in the engine so as to eliminate the pressure switch, grounds and or wiring?

There are aftermarket oil pressure gauge kits, I have one I bought many years back for mine to check it.

Bountyhunter, is it possible the oil pressure switch is defective or glitchy?
it seems unlikely in this case, but you never know sometimes. ???