Post top-end troubleshooting my KZ750 lawn mower

I've got a doozy of a post here, but any guidance would help a LOT. I did a top end job (*beams with pride*). The cylinders were honed and I got new piston rings. What I know and think I know:

-Before this work, the bike sounded like a 36-cylinder sports car. BZZZZZZZZ. Or a battalion of bees.

-Getting it to start was a huge pain. The battery was dead so I push started it until it went.

-The oil pan is leaking like a madman from the side under the window. I can't isolate the exact spot, probably because it's a full two inches of leak.

-In installing the exhaust, I stripped two studs. Those studs are WAY too short to work with the gaskets that came in my Vesrah set, so I may replace them all with long M6 bolts cut to size (I tried one and it works like magic). I'm currently running with one nut off the exhaust.

-The bike now sounds kind of like a lawn mower, not like it used to, but is not spewing smoke out of the exhaust manifold, so I think the seals are decent enough.

-I hear clicking. My guess is valves.

-There's no power until about 4k RPM, then it wants to go somewhat. Even after I tricked it into warming up, I couldn't let off the throttle or it would die. I tried futzing with the idle screw, and it changed nothing. Once I revved it up to 4k or so, it settled down to idle very slowly, as if it had a super heavy flywheel that didn't want to stop.


Here's my guess at possibilities:

I might have gotten the green/red leads switched at the ignition coil, so I'd only be firing on two cylinders, right? If not, what's with the huge lack of power and strange behavior?

I probably tightened the oil pan incorrectly. Should I have put gasket sealant all the way around? Is it irrecoverable now that it's started pouring oil out or can I salvage it when I change oil in 50 miles?

It sounds like there is several things going on. First charge the battery so you can do some testing.

Second, what all did you do in the top end job. When you had it apart did you bench check valve clearence. When you put it back together did you get the cam timing correct? Have you done a compression test? Did you clean and lube the spark advancer?

You think it is only running on 2 and not on 4. Check this out but testing for spark at each plug. Do the exhaust pipes get hot, spray some water on each one and they all should sizzle about the same. If not then the one(s) that do not have an issue.

Did you check carbs and clean them. Are the carb holders tight on the head and carbs with no leaks.

Ticking sounds can be valve, or timing chain, or an exhaust leak.

As to the oil leak, you make is sound like it is leaking quite a bit. If so I would drain the oil, drop the pan, clean it up and look for issues at the leak area, use a new gasket and put it back on correctly.

Battery charged. The starter works! But doesn't start the bike.

I also isolated the source of the oil leak. The cables running out of the pickup coil got snagged in the oil pan. This could explain more than one of my problems...

Either by being pinched, or in the process of unpinching them, I ripped through the yellow wire and possibly the red. I've got some soldering to do.

The oil pan gasket looked fine (untouched, even), so I'm gonna try reusing that unless you think it's a terrible idea...


I also replaced one of the exhaust studs with a stainless steel M6 bolt cut to length. It works like a dream, but now I'm worried it'll react with the aluminum. Anyone have any guidance on this?

The crimped cables did, in fact, cause two of my problems. I cleaned them up, soldered them, covered them up and re-routed them away from the danger zone. Now the bike runs like a dream and I've started beating it up.

I pulled all the exhaust studs. It was such a pain. Most of them were seized. I had to dremel two of them flat so a crescent wrench would turn them, because the vice grips were stripping them.

I replaced them with stainless steel. I've learned there's a tendency for SS and aluminum to hurt each other, so I'll probably swap those back out for galvanized at some point relatively soon.

But I am a very smiley, happy man.

Glad to hear you found the problem and solved it. Just for future reference, if the threads are good you can use to nuts on the stud one as a lock nut tightened aginst the other to turn them out. Yes steel and alum do have issues but there are some chemicials you can put on the threads to lessen this.