Having trouble leaning out my mixture [KZ200]

Hi, I've been using google as my main source of info into fixing my 78 KZ200 but this time I'm really stumped and thought I'd ask. So basically my problem is that I can't get the bike to idle at all. I've replaced the coil, cleaned the points, adjusted my timing and replaced the spark plug. The bike has a strong spark and the compression tested within spec of the manual. Basically what will happen is the bike will crank up with a new spark plug and idle pretty high. However, in the course of about 10 minutes, the bike will gradually require more and more throttle/ carb adjustment to keep from stalling. And once she warms up, the bike will almost always stall. It fouls the plugs with a dark sooty substance and prevents them from working anymore.

So it's running pretty rich. But I can't seem to get it to run any leaner. Stock exhaust, Keihin carburetor, stock pilot and main jet size. Carburetor is adjusted to leanest possible settings, air screw turned out, idle adjustment turned in, needle all the way down, and it shows the same symptoms. Even taking the air filter out and running the bike doesn't show much difference. I've also adjusted the float height to a little lower. Is there anything I'm missing or probably doing wrong? I'm pretty novice but I've really been doing some research and can't seem to find any issues in my method. :huh: Thanks

Open the bowl and see if the main jet or pilot jet fell out. That happens sometimes right after a carb rebuild.

If the carb hasn't been rebuilt in a long time, it's possible you are idling on the main circuit (instead of the pilot circuit) because the pilot circuit is clogged.

Another possibility is the carb is overflowing gas into the engine. Normally an overflow will drain out of the carb's dedicated overflow system, but if that is clogged, the gas has nowhere to go but into the engine. As the engine warms up it will run worse under this condition.

Thank you. I'll check the overflow tomorrow to see if it's clogged. I rebuilt the carb with a rebuild kit when I first got the bike and have since taken it apart a few times after that. I'll also adjust the float height as low as the bike will allow to see if there's a difference. I didn't mention this before, but I have gone through the charging system which is outputting around 13.5 volts at idle which seems adequate. The bike is rideable but at a significant power loss and only if the throttle stays open at stops.

Sounds electrical. Hows the battery and the connection from the coil to the plug? Also, you should disconnect and clean every single electrical connector on the bike. Lots of issues with those.

Check the carb holder and valve adjustments.
Steve

Thanks. My gasket set came in today so I took the head off and unfortunately lost one of the cam sprocket screws into the crankcase :pinch: Have to go fish it out over the next couple of days. There's also a lot of carbon on the valves and valve guides and I don't have the tool to remove the valves. Would seafoam be a good way of cleaning up some of the deposits while I have it dis-assembled?

Valve guide seals. A C clamp and a piece of PVC cut out can make a valve compressor. Just use a deep socket to dislodge the keepers first.
Steve

Why did you take the head off? Why remove a cam sprocket?

I saw a gasket kit online and thought I could give the top end an overhaul while cleaning and checking that things are in spec. At this point I've really just cleaned it up really well.

When I was burning oil due to bad valve guide seals I had to go down one step on the pilot jets. Almost like a two stroke. Pics, need pics.
Steve

Wow. From mixture problems to overhaul in one tiny thread.

SQUIRREL! :woohoo:


I hope that gasket set was made in Japan. There are some pretty crappy ones out there.

TexasKZ wrote: Wow. From mixture problems to overhaul in one tiny thread.

SQUIRREL! :woohoo:

Haha this bike allows the head to be removed with the engine still in frame so it's not too bad. I'll try and get some pics tomorrow or Saturday.