TOPIC:

Ok guys I’m back. I’m not stupid and have built a few auto engines in my life. I understand there is a difference, this is why I’m asking you. Please allow me to try to explain without all the criticism. I disappeared because I have a job and can’t work on my bike every day. I was riding the bike and the oil light came on and then it acted as if it lost a cylinder or something immediately. As I said it was almost like it isn’t getting good spark, but that didn’t make sense to me because of the oil light. Will not start by ignition but will start by (jump start) but have to stay on the throttle to keep running. But even then it runs very poorly. I agree that it all sounds like a bad fire somewhere but doesn’t explain why this all started with the oil light coming on while riding and then immediately as oil light appears wants to die. I changed the oil and filter today with the proper oil and levels. Someone told me to look at the oil sensor but would the sensor make the motor run poorly? If the oil light comes on is there some kind of safety thing I don’t know of that will kill the engine? I didn’t think so being people have rode with the oil light on for extended periods of time. My bike died while riding immediately after oil light came on. And I don’t believe there is a mechanical problem. Could use all your help, even you Old Kaw if you have any direction. I’m not on here everyday but will stay in touch and look forward to all suggestions. Thank you very much! BR

Sorry I forgot to answer the question of starting. It does turn over but will not fire. Also battery great for the better than us, no ones that need help. As I said, this all started with the oil light coming on while riding, then immediately dies on me. Thanks to all who can give direction instead of criticism.

I would pull and clean the oil pan and check the oil pump and filter screen is been clogged. Any start of the engine now can destroy your crank and rod bearings.

BR wrote: ... then immediately as oil light appears wants to die. ... My bike died while riding immediately after oil light came on. ...

This is slmjim,
Not familiar with the 750's but, maybe OP and us (the forum) need to look at what's happening and not what we're seeing. To wit:

An electrical circuit (oil pressure indicator) energizes (malfunctions) without apparent reason and, at the same time, a different electrical circuit (ignition) malfunctions.

Consider the possibility that the oil pressure indicator being energized might be a red herring, and that an electrical short, open or poor ground could be responsible for both symptoms.

Undoubtedly, correct oil pressure should be confirmed for obvious reasons. It just seems suspicious that two separate electrical systems would malfunction simultaneously.

Not being familiar with the 750's I can't really offer advice past what I've written and, admittedly, I may be off base completely. My early career as a Tech in complex electro-mechanical devices (photocopiers, printers, MFP's etc.) led to learning the concept of "look at what is happening, not what one is seeing".

That's all I or The Lovely Z1BEBE have to offer at the moment.

Good Ridin'
slmjim & Z1BEBE

The motorcycle needs a good, fully charged battery to run right. I would charge the battery with a good motorcycle smart charger & do a load test. You may also need to check the charging system. There's a good pdf manual available for the 750-4 chain drive models >> gold cover w color wiring diagrams (there's also a poorly copied pdf, so get the good one).

If the bike still has the old spark plug wires & ignition cols, I would either redo all of the spark plug wire connections or go ahead & get new. At the coils unscrew the ribbed compression boots. you can re-use the sheathing & o-rings n stuff on new plug wires for a waterproof fit. When re-using the old spark plug wires, nip off the ends a tad >> the wire tends to oxidize at the connections.

If you get the bike running & fully warmed up, you can check the coils to see if they're getting hot. they should be warm, not hot. mine were very hot to the touch.

Engine oil light. There should be ohm tests in the service manual for the engine oil pressure switch. You could also disconnect the wire & install a test warning light to see if the switch turns off the test light when the engine is started. this would be an easy thing to do using a 12V test light.
...

Given all the evidence I would look at the oil pressure switch shorting on the points / ignition plate. If the live to the oil pressure switch is earthed by either the switch with no pressure or it earths against the crank cases or ignition plate the oil light will come on. If it is shorting against something on the points / ignition plate there is a likleyhood it would kill the spark causing both symptoms with one fault.

BR wrote: Someone told me to look at the oil sensor but would the sensor make the motor run poorly?

Please see Warren's answer. In his scenario, a wiring short under the ignition cover could cause strange things between the ignition and oil pressure warning light.

BR wrote: If the oil light comes on is there some kind of safety thing I don’t know of that will kill the engine?

There is no device that would kill the ignition intentionally through the oil pressure light system. The oil pressure light is a simple light-bulb circuit and that is all.

At the very least, you should pull the ignition cover and inspect the wiring. The oil pressure sensor is located under the timing plate. It would be almost unheard of, but not impossible, and luckily easy to check.

BR wrote: Ok guys I’m back. I’m not stupid and have built a few auto engines in my life. I understand there is a difference, this is why I’m asking you. Please allow me to try to explain without all the criticism. I disappeared because I have a job and can’t work on my bike every day. I was riding the bike and the oil light came on and then it acted as if it lost a cylinder or something immediately. As I said it was almost like it isn’t getting good spark, but that didn’t make sense to me because of the oil light. Will not start by ignition but will start by (jump start) but have to stay on the throttle to keep running. But even then it runs very poorly. I agree that it all sounds like a bad fire somewhere but doesn’t explain why this all started with the oil light coming on while riding and then immediately as oil light appears wants to die. I changed the oil and filter today with the proper oil and levels. Someone told me to look at the oil sensor but would the sensor make the motor run poorly? If the oil light comes on is there some kind of safety thing I don’t know of that will kill the engine? I didn’t think so being people have rode with the oil light on for extended periods of time. My bike died while riding immediately after oil light came on. And I don’t believe there is a mechanical problem. Could use all your help, even you Old Kaw if you have any direction. I’m not on here everyday but will stay in touch and look forward to all suggestions. Thank you very much! BR

If you are referring to me calling you stupid, I said nothing of the sort. And with now with a grand total of 5 posts, no one knows exactly what you do or don't know. I totally understand having responsibilities and a job.

You posted very little info in the prior 3 posts you made, and seemed to be flying off on a tangent with oil pressure tests before I brought up the battery question. Every new post goes off in a different direction,. If it will start jumping it off of a car, so that kinda points to battery capacity, rather than oil pressure and wiring issues. The oil light circuit is a pretty simple. And like almost every sudden change in how a bike is running, there is likely one thing causing it.

Anyway, since you feel confident in your mechanical abilities ,and are an accomplished engine builder, this will be a piece of cake cake for you.

I'll be the bad guy here. does the engine turn over slowly when trying to start it? Unlike the 82 GPZ750 which has an oil level light, the oil light on these comes on when you lose oil pressure. If it came on while riding then stopped running and now won't start without a jump then runs like crap I would say there is internal damage to the engine from lack of oil pressure. The first thing that goes bad on this engine when it loses oil pressure are the camshaft journals. The next system to fail are the crankshaft plain bearings.
I would do what others here have advised regarding checking the oil pressure the pressure switch and it's wiring just to eliminate it and it's easy. If it checks out your going to have to start taking it apart starting with the oil pan to inspect for debris

Good advice. Pretty brutal, but solid advice. .. As everyone pries feedback info out of BR. Oh.. it came on >THEN< the motor died. lol

The oil pressure switch is easy enough to check with a test light as others have suggested. . It grounds the light to come on ( not familiar with this bike, but know how the oil light circuits work), hooking a test light to the positive post on the battery, then touching it to the terminal on the switch while running, the light should be out. It should be on with no engine crank. OR unplug the pressure switch and see if it goes out.

It surely will run like crap for a minute or two then seize if the bearings are shucked. Was it run low on oil? You can verify internal engine damage by dissecting the oil filter and draining the oil into a pan looking for bearing material / metal shavings. Hope this isn't the case. With only 12K miles on this motor, it should be nowhere near worn out, something would have to cause this.

If bearing damage was bad enough to make the engine run rough or even stop it running at all you would hear it. Take the plugs out and spin it over and see if it will spin over ok without any unwanted noises emitting from it. If it does then its unlikely to be anything too catastophic. If it does make horrid noises spinning it over with no plugs will be the least of your worries as it'll need a strip to investigate anyway. These motors are pretty bullit proof. The electrics on the other hand...... investigate the easy stuff first, battery, oil pressure switch wiring and any wiring in its vacinity before ripping out the engine. I suspect a combination of a couple of faults.
We need more info from BR.