Hi guys looking for some help with this thing. im pretty mechanically minded but stuck on this one i have a 1997 kx 250. Starts 1/ 2nd kick everytime. runs and revs to 3/8 throttle then just pops and bangs missfiring like anything. had the carb cleaned 3 times new air filter reeds are ok. new plug. sent the stator off thats ok. Cdi??? Powervalves all moving freely exhaust is clear. tried another coil off the same bike that my mate has. jetting is 168 45 im at sea level. put a new piston in the bike ran it in went to ride it seemed ok draines oil etc replaced.then all of a sudden this happens?? Any help would be much appreciated ive spent £££s now and its makin me angry :-[

 

Any help guys???

 

Hi all ! Your post is a little confusing . Did it run ok and then you put a new piston in and now it runs bad?

 

It does sound like something changed after you replaced the piston.

What does the plug look like? If you have done all of the above that you listed, check the plug wire since you have already checked the coil. Is the piston installed/placed correctly? I would be curious and tear this gal apart for inspection.

 

Still sounds like a plugged jet. When you say the carb was cleaned 3 times, is it possible that the jets are still plugged with crap? Did something fall out during the first clean?

 

did you figure out what the issue was? I have similar problem with a but newer bike