Re: NEED HELP!! '81 cb750c wont fire!!

Posted by mallen14 on May 01, 2012; 7:10pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/NEED-HELP-81-cb750c-wont-fire-tp3950861p3953538.html

Sorry for the confusion but I HAD spark on cylinders 2&3 before I broke the wire running to the generator for those cylinders. I still have spark on cylinders 1&4 though. But I bought a compression tester and came home to use it.

Ok so results are in and problems that I know about are...

1) Pulse generator wire was fragile and broke while inspecting it. Will try to solder the wires back together later but right now that's why cylinders 2&3 are not firing.

The main problem...
2) Compression test shows the following: Cyl 1=60psi Cyl 2=58psi Cyl 3=0psi Cyl 4=56psi. Also put in small amount of oil in cylinder and pressure shoots up to 150+psi which means new rings right?? Or could the valves somehow cause this?? Also Im guessing cylinder 3 has a bad exhaust valve(maybe stuck open allowing no pressure to build up).

After the compression test and oil in the cylinders(to add some pressure), I squirted some starting fluid into the engine, replaced plugs and wires, and tried to start it again. Of course it didn't start because only two cylinders are running, but it was firing and blowing smoke out the tail pipes. This makes me think now so much a spark issue as compression issue.