1978 kz750 smoke

The mystery oil they have on the shelf is a additive. I was looking for the old school oil but OR didn't have it. I needed it for my assembly oil formula. I used it instead. It worked.
Steve

When you say rings are stuck do you mean they are stuck to piston and not compressing against cylinder walls

Oil and carbon can turn into a gummy substance so the rings won't expand like they should. If it sits for a long time, they can gall the cylinder walls and even distort the ring lands causing problems. It is a good idea to squirt a small amount of oil into the cylinders at start up to prevent this from happening.
Steve

Soxx4u wrote: When you say rings are stuck do you mean they are stuck to piston and not compressing against cylinder walls

Exactly, the rings need to move in the ring grooves, also they rotate slowly at about 1 rpm. You might get lucky and they can be freed up with some solvent or oil in the bore, followed by a good thrashing - or you might have rusted bore. When a motor is left for years, the pot with a valve open gets condensation in the air causing rusting in the bore.

Damage to the cylinder walls, a broken ring(s) or just bore/rings/pistons worn out of tolerance...quite a few possible causes, all the usual suspects on an old bike. Always worth running it for a while if it has been standing unused for any length of time as there is a fair chance it will improve.

I have one new piston and one fairly new and have rings ang valve guide seals coming. Do you think that would fix my problem. And can I get a hone tool at harbor freight

You can get a hone at OR or AZ. I use the course stones not the de glazing stones that come with it. The idea is to make them seat right now. Once you get the head off and the valves out, you will check the seats, guides etc. and go from there.
Manual?
Steve

Or= Orieleys auto parts?
Az= auto zone?
I have the disassembly section of the manual not the maintenance.

Yup. You really need a manual.
Steve
BTW, whenever I had a bike come into my shop, I always bought a manual if I didn't have one. Just the cost of doing business.

Dry test 50 psi wet test over 200 psi. All other pots around 150 psi, engine tested cold.



New pistons, rings and rebore time at 45 000 miles? maybe not.

gpz750 had only done about 800 miles in previous 10 years, I've done about 500 miles now in a month after recommissioning it and it runs great, I will retest compression soon. I think the rings were gummed and I'm hoping the solvent soak and thrashing will improve or clear the problem.

You've had my advice, what I try firstly in the same situation...

Thank you for the help I should be getting the rings on Wednesday. Just pulled the motor and will start disassembly. I'll kepp you guys up to date with what I find inside

ok good luck , you seem to know exactly what you are doing here.

Usually stuffed bores/rings would yield blue smoke, perhaps with some exhaust smoke coming out of the oil filler cap caused by blowback gases. On aircooled motors white smoke is usually condensation....

The other point being if the bore is damaged beyond honing, unless you can find another servicable block - or press a new liner in, you'll be needing oversize piston(s) and rings anyway.

Update... I pulled the motor. Tore into it and found that my oil ring broke in three pieces. One is in the crank case hopefully I can find it without splitting cases. Pistons look good cylinder walls look good. Thank you all for your help.