Bad news! Right cyl. blows smoke, compression low

Had the KZ400 out for a short ride today. Seemed a little down on power, wasn't idling particularly well. Noticed it blowing a bit of smoke when I brought it back home before I shut it off. Figured I'd pull the plugs and take a look. Right side plug looked a little oily, left side looked dry. I hooked up my compression tester and confirmed my worst fears--60 psi on the right, 142-ish on the left.

Bike has low mileage, it sat for years before I bought it. Had to break the engine loose with WD-40 and patience.

So, I guess my question is, what do I do now? I re-ringed a Dodge Neon 2.0 4-cyl. earlier this year. Is the KZ easier or harder?

Sorry, but I'm a noob when it comes to 2-wheeled vehicles. :blush:

The KZ will be a lot easier. Half as many parts and they're all smaller too.

Would first assure valve clearances being to specs. Then re-test compression.

Exhaust smoke might possibly be from poor spark quality (related to some ignition issue), or from carb issue such as too high floatbowl fuel level, leaking float valve, sticking or leaking float.

Black smoke is typically from unburned fuel mix.
Blue smoke is typically from worn oil ring and cylinder.

A leakdown test could indicate whether there's blowby past the compression rings into the crankcase, or through a leaking valve seat, or blown head gasket.

Good Luck!

if you had to break it loose with wd-40 i'd say it's a good bet that there is rust grooves cut in to the cylinder from where the rings sat in the cylinder in one spot and rusted in place ,it will most likely require an overbore.

What manual is best for the KZ400? Looking on Amazon, I'm leaning toward the Haynes since it seems to cover a narrower range of years and models. Clymer seems to try to cover more. Anybody have a favorite?

Would hold out for the official Kawasaki Motorcycle Service Manual covering the specific model, which is imo far superior to any of the aftermarket shop manuals.

Could check ebay.

Good Luck!

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Wonder why the ebay tags aren't working on Firefox?

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I would definately go for the Kaw manual over the Haynes or Clymer.

Keep us posted on the engine work and take pics for us!

At 60 psi, that cylinder is not burning the fuel so it might look black out the pipe. Check valve clearance. If it's OK, you have to pull the head.

A kawi manual is a MUST HAVE before you try to rebuild it.

Well, I've recently gotten compression readings up to 80 psi. Adding oil via the spark plug hole does not seem to have any significant effect on the readings, so I'm leaning toward valve seating as opposed to rings. I know the carb on that cylinder isn't right, and the plug is kinda dry black looking.

I adjusted the valve clearance. It was a little tight, but just a little. Set within specs now.

By shining a flashlight in the spark plug hole and pulling the exhaust and looking in there, I find a lot of black carbon.

Smoke is more black/grey than blue.

Got the manual via kz400.com. Nice site.

Well, by now I assume you all think I'm a moron and gave up on me. If not, here's proof! :laugh:

I rode her again this morning. Seemed a little better at times, but tends to surge at cruise. Noticed that the idle seemed more consistent. Decided to check the compression yet again, with the engine hot, and after reading through the manual, remembering to crank the throttle wide open--which is something I had not been doing previously. Doh!

What do you suppose I got for a reading? The notorious right cylinder checked in with a 170 psi reading. Slightly amazed, I re-checked with the throttle closed--80 psi. Doing the same thing on the left side, I got 180 wide open and like 170 closed.

So this of course brings me back to the carbs, which I knew all along needed help. Apparently, the left cylinder is sucking enough air through the carb to get normal compression readings with the throttle closed, while the same passage(s) in the right carb are totally clogged up.

So... looking for yet another set of antique Keihin carbs.