I've got a Kawasaki Bayou 220 in my shop that I can't figure out. It is running way too rich (the plugs are running soot black) and, while it will rev up relatively fine without the airbox installed, once you get the airbox snorkel even close to the carburetor intake, it bogs down. When you rev it up, you can see gas spewing out the carburetor.

I have been through the carburetor a dozen times. I have checked, re-checked and triple checked the jets (the original main jet had enlarged a bit) -and- (aftermarket jets are not always what they claim to be). I even went so far as to get a new aftermarket carburetor just to use as a body if I had to and still get the same results.

With the gas spewing out the carburetor when it's running, I suspected an intake valve so I checked timing. The timing chain tensioner was extended it's full length, but the chain was still way too loose. Just as a test, I let the tensioner extend past it's limit, which put tension on the chain again. I did move the chain one tooth, because it looked like it had jumped. Still get the same results.

Finally, I ran a leak-down test. With the cylinder at top dead center, sure enough, there is air leaking out the carburetor. Just to make double sure, I rocked the crankshaft back and forth and nothing sealed the valve. Apparently it has a leaky intake valve.

tl:dr; My question, I guess, is can a leaky intake valve cause a rich condition and and if so, how?

 

Wouldn't have thought so but it needs the valves sorting, and a new cam chain, so do them, try it and come back to us with the results. Check ring gaps while you have the top end apart too.