OIL LIGHT ON at low RPM

I have a 1973 z1, and my oil light comes on at low rpm around 900-1100rpm range. Can anyone tell me what might be the problem, the bike sound and runs great but the oil light kind of worries me. Please let me know if this might be some simple problem..

It's possible the oil pump gears are worn. Another place to look is at the pressure sensor. I believe it's under the sprocket cover or behind and below # 1 cylinder. It may be failing.

These engines have roller bearing cranks with oil pressure about 2.8 to 3.0 PSI. Can you put a low pressure gauge on the fitting above and behind the points cover? This will tell you if the oil pump needs repair.

Any history on the bike?

Have you owned it for very long?

Another cause, I've see that happen when an oil pan was put on without the O-Ring around the filter cavity.

the engine was fully rebuilt from the base gasket up, new piston rings and much much more, but the crank case was never touched; I did pull of the oil pan and clean everthing in down there, It was realy dirty and I found all kinds of stuff, the oil pump filter had tons of dirt on it, I turned the oil pump and it did pump oil through it; And I cleaned the oil pump filter, So I cleaned everthing I could on the top end and in the oil pan area; I drained the oil after running the bike for about 10 miles and put in new stuff again just incase. But the oil light is on again, I took the bike for a 30mile ride and all sounds good, but now the oil light comes on around 3000rpm and anywhere below the 3000rpm range when the bike is hot. Let me know if anyone has an idea about this. Also what oil filter oring are you refering to in your last post.

how many miles on bottom end?....probably needs a pump...
you can blow 60 bucks and get a guage that mounts on right side of motor and get a real number to see whats up....

Maybe this will help... Right out of the manual...

Thanks i will hook up the oil presure; I bought one so I will test it out to see what the presure is, but if all is good than I don't know what to do next.....

One thing I find interesting is the 3000 mark in what you're seeing...

"At or below the 3000rpm range when the bike is hot."

As can be reviewed in the attached instructions, this is the exactly rpm range for the service limit confirmations...

When you ramp up to 4000 rpm or so, you should measure easily 10 psi or more...

I just went through this in my project, I got my replacement off e-bay for ~ $20...

NOTE: Oil pump parts are not available, as written in the manuals, you replace as a whole unit...


Let us know how it works out for you... While in there, replace your o-rings and gaskets....


OMR

I was hoping that I wont have to pull the pan again but I think I will have to do it, I have an other oil pump, but is there anyway I can test the pump??? I don't want to pull the pan again, there is just too many bolts on that thing

"is there anyway I can test the pump?"..

Already provided in my first reply.... If your pressure is within specifications as depicted in the manual excerpt, then you're most probably good to go regarding the pump itslef...

But... if you lost one of the O-rings, or it's bad and not sealing then your pressure would be off...

Is oil being pulled up into the top head/valves?
See oil flow diagram....

Also, have you removed the oil light switch sending unit (back side of cylinder) for cleaning and testing?
Basically all this unit is is a pressure transducer that switches ground to the instrument cluster when low pressure is recognized.

Do you have a good & strong ground to the motor itself?
This is required for the sending unit to work properly...

OMR