Engine problems and I'm stumped! Help please!

[ryanthamilton7]

I bought a kz200 a few months ago and I've been building it up as a cafe/tracker. The bike was running when I bought it but not well. I have since cleaned the carb, changed oil & filter, replaced the plug, adjusted the point gaps, and set the timing. Throughout the build process the bike has been running on and off. Sometimes it would crank immediately and run well, others times it would not start at all.

Today I tore down the carb and gave it another cleaning. I checked the point gaps and timing again. I checked the plug to be sure it was sparking. The bike cranked up and I adjusted the idle and air screws on the carb. It was running better than it ever has, idling well where previously it would die if the idle wasn't high. I took it out for a spin and it died while coasting to a stop sign about 1/2 mile from my house. Then it wouldn't crank again. After pushing it home I try to diagnose the problem. I Pulled the plug and it was quite black and not sparking. I replaced the plug, got a spark and the bike still wouldn't crank.

I'm very confident that there is not a problem with the fuel/carb. I think this is a spark issue but when I test the plug I'm getting a spark. I'm at a loss here. I'm thinking that it could be a weak spark and it's not sparking with the compression of the engine? The plugs also seem to be fouling but I don't see how that's possible within 1/2 mile of riding, although there is a very small amount of smoke coming out of the exhaust.

The strangest thing is how the bike will run well one minute then it will not even come close to starting. It wasn't even sputtering after this latest incident. If anyone has ideas on what to check next please fill me in. This is driving me nuts!

 

[Hot500]

When you say you got a spark but the motor wont crank, do you mean the motor will not turn over, or that its turns over but wont start?

Is this bike electric start or kick start only?

I'm thinking you may have a fuel problem. The symptoms you describe sounds like the bike is running very rich. You say you cleaned the carb, but did you put a new kit through it. New jets, needle and seat, gaskets etc. If the needle and seat is worn the carb will flood. It wont like to idle and will blacken up the plugs. When you try to start it the plug electrode gets saturated with fuel and wont carry a spark. The bike will run like a three legged goat at anything but high revs.

Try to start the bike and quickly take the plug out and have a look at it. If its wet its flooding. Get a carby kit. You didn't mention the air filter. Make sure its clean. If its old, get a new one.