KZ750 Cylinder 4 dead

I finally got it running and thought it was just miss firing on a cylinder but seems to be not firing at all. Cylinder 4 is dead as far as I can tell. I pulled the plug wire on it while running and it did nothing dfferant than what it's been doing. It has been running on three cylinders the whole time.

I have tried putting marvel mystery oil in cylinder,fuel and engine so I can loosen whatever problem I have. Thinking it was a ring but hoping for a stuck open valve. I'm running out of idea's to try but I will fill cylinder again with marvel to see what happens. I think this is my last option before rebuild.

Last compression test was 60psi on cylinder 4 but will retest all cylinders one more time before rebuild.All other cylinder have 180psi but I need to check again. I have put engine oil in 4 and does go up to about 90psi ;so everything points to ring problem so far.

If you have any tips I would like to here them. I'm not against rebuild just want to make sure I'm checking all options first and don't want to find out during tear down that it was something else. Do you think anything like engine honey or liquid cylinder type repair products would help? If I could get psi higher so it would fire I would have a better chance of it fixing itself; hoping it is a stuck valve or something.

Thanks
Ray

with that low of compression, I dont think its gonna fire, and if it does it sure isnt going to be right.
I am guessing you have checked the valves and they are set ok?
the down side , not much you are going to put in the cly is going to free it up enough to run right

Leakdown test should help determine exactly where compression is escaping.

With #4 plug wire connected to a brand new spark plug with plug base held against engine head and engine spun over with ignition switch on, what if any spark quality is visually observed at the plug tip?

Good Luck!

Good spark! First thing I checked when I noticed it was not firing. I always look at first thing spark, fuel and air equals motor will run it might not run good but it will run.This would also mean you have good compression and right now I don't.

I do need to try leakdown test and no I have not set the valves. I will check valves and see if I can make up the leakdown tester and give it a try.

Thanks
Ray