Top End Rebuild on KZ650 -- Should I bother?

Hey all,

So I was thinking of doing a top end rebuild for the following reasons:

1) White smoke from exhaust and out crankcase breather
2) Oil leak-down test gave me higher compression (disputed method, I know)

But my compression is not that bad, especially considering I didn't even do it right.. 1-4: 130 130 120 125 (cold engine, closed throttle-- whoops will redo). Valve adjustment was done last winter.

From what I've read, it could be either the valve seals or piston rings, and I can change both if I open up the top end. Obviously, I'd prefer not to open it up but it's clearly burning some oil somewhere!

Also, my plugs are straight black even though by every other metric my bike runs lean. Still sorting out the jetting with the pods, and planning on doing the WG coil mod.

I suppose I just need convincing before I drop >$200 and many hours to a rebuild.

What do y'all think?

- Stephen

Do a warm and proper comp test before making any decision. If the throttle was closed, the test results are meaningless.

If the motor is not leaking oil, and the plugs are not getting oil-fouled, and comp is within range, there is only potential (and likely) downsides, and no upside.

If you are eager to work on a motor for education etc. I would get a basket case non-runner Kz650 to fix up.

Old oil will also make the bike smoke.

loudhvx wrote: Do a warm and proper comp test before making any decision. If the throttle was closed, the test results are meaningless.

If the motor is not leaking oil, and the plugs are not getting oil-fouled, and comp is within range, there is only potential (and likely) downsides, and no upside.

If you are eager to work on a motor for education etc. I would get a basket case non-runner Kz650 to fix up.

Totally planning on redoing the compression test! It's just freezing here in Chicago

My plugs are definitely fouling ... guess I should maybe run the engine for a while and pull the plugs immediately to see whether they're wet or dry? They are black though.

I suppose I just don't see how my fouling can be a symptom of running too rich, since I have pods and if anything [strike]all[/strike] most other signs point to it being too lean. (pilots up to 17.5, mains stock 102.5, stock exhaust). Does another possibility exist? Maybe insufficient spark if my coils aren't getting the necessary voltage?

Thanks for the help!

baldy110 wrote: Old oil will also make the bike smoke.

It's been smoking out of the crankcase breather since the day I bought it, even after several oil changes. But also have been getting lots of smoke out the exhaust too.

Smoke out of the crankcase is probably just condensation.

It's a old bike. Valve guide seals harden and become brittle. I lived with this problem for a year until I could gather the parts for a valve job. New valves, springs, viton seals, no smoke, fouled plugs and my valve train sings like it did when new. A chance to inspect the bores too.
Steve
kzrider.com/forum/2-engine/597268-81-kz1000-burning-oil#662797

Some blow by smoke out of the breather is normal. The thing shouldn't be blowing major smoke though. Sorry but I'm not sure how to describe the difference.

I live near your hit and run, so I know your pain about the cold.

I thought you mentioned it running differently after the accident, is that correct?

A little smoke is normal from the breather. As long as its white its probably mostly steam. On a hot day, when the motor is hot it should be clear. If its definitely blue, then its oil burning.

If one part of the jetting is rich, and the rest is lean, you can end up with carbon, even though its lean most of the time. You really need to figure out if its oil or carbon. If its wet, then you need to figure out if its oil or gas.

There is a place in ukranian village that has indoor storage, and has a full shop if you need to do work indoors. My buddy works there on other peoples bikes some times. It's pricey but has lifts and power tools etc. It's called motoguild.

loudhvx wrote: I live near your hit and run, so I know your pain about the cold.

I thought you mentioned it running differently after the accident, is that correct?

A little smoke is normal from the breather. As long as its white its probably mostly steam. On a hot day, when the motor is hot it should be clear. If its definitely blue, then its oil burning.

If one part of the jetting is rich, and the rest is lean, you can end up with carbon, even though its lean most of the time. You really need to figure out if its oil or carbon. If its wet, then you need to figure out if its oil or gas.

There is a place in ukranian village that has indoor storage, and has a full shop if you need to do work indoors. My buddy works there on other peoples bikes some times. It's pricey but has lifts and power tools etc. It's called motoguild.

Well hey man! I actually have a garage in Logan now, you should swing by!

I thought the bike wasn't running after the accident-- with taking a direct hit to the engine and all-- but I actually got it started with some minor persuasion.

Before cracking open the engine.. I decided to first do the Wired George coil mod, just to see if that would clear up my sooty plugs + my coils weren't getting proper voltage. aaaaand now it doesn't start. No spark even. Must have messed something up, but likely will start a new thread for that problem haha.