Have 1987 KDX200 that runs as if choke is always on, and obviously blows lots of blue smoke. Also fails to idle, and strangely turning the idle adjustment all the way in has no effect. Ran fine before being garaged for many years. The carburetor has been disassembled and thoroughly cleaned (twice). The choke circuit and mechanism are fine, and idle adjustment raises the slide properly. Has brand new air filter and spark plug. Using proper gas and oil ratio as well.

Bike fires right up with two kicks and runs ok, except it burbles, does not have full power and lots of blue smoke. The symptom is just like you left the choke on. I have swapped carbs between two identical KDX200's. The suspect carb ran great on the 2nd bike.

Does seem to have a weak spark. However, past experience with poor spark, the bike would be difficult to start. This bike starts quickly every time. Once when first troubleshooting this issue, it suddenly cleared up and had great power for a minute before it went full throttle on its own and ran out of gas. Thanks for any help and suggestions.

 

Unless your "thoroughly cleaned" includes a good carb washer or ultrasonic cleaner, you may not have gotten it cleaned out properly. The idle circuit is clogged up - that is what will run the bike from idle to about 1/4 throttle. It it difficult to get cleaned out. When I worked at a bike shop sometimes the mechanics had to do a carb set twice, with the bodies in the washer for several hours. The cleaner has to get into the passage and dissolve the gum or wash out whatever is there.

The idle circuit is a very small passage, clogs easily with crud from the float bowl, usually crud from letting the bike sit long enough that the gas in the carb dries out. When fresh gas gets mixed with the flaky junk in the bowl it turns to a gum, washes up into the pilot and now the circuit is blocked and won't work.

Try getting the carb body washed at a shop or auto shop that provides the service. Shouldn't be expensive, since that part isn't labor intensive. You do the rest yourself.

 

check crank seals and the reeds for fraying at their corners. also check for at least 150psi compression. and take off the silencer and blow through it. If it presents any resistance then it needs to be taken apart and cleaned.