I bought an 02 250 2x4 for my wife with the understanding it had some issues. It cranks and idles great. At around 1/3 to 1/2 throttle it starts to hesitate and bog. Sometimes it will clear up and rev higher to almost full throttle. Sometimes it tries to die until I let off the throttle. Usually it makes it about half way to WOT and just stumbles there. I have cleaned the carb until I don't know what else to do with it. I put in a new plug this morning and pulled it after maybe 5 minutes of idling/riding. I was expecting a clean plug or white color from running lean, but what I got was a black soot covered plug. I'm pretty sure this means I'm running rich. Do I have an ignition problem or am I missing something? As far as I know all the electrical components are original. Any help? If it is an ignition problem, where do I start testing? I did replace the boot from the air box to the carb. It was torn and I was hopeful that this would help, and it did a little I guess, but still having some issues

 

Run a compression check, if that is ok then buy a spark tester, they are cheap and test for a nice blue spark that can jump a 1/8 gap. If that is good then buy a good rebuild kit for the carb, make a thorough rebuild and set to specs shown in rebuild kit. Just a ceaning rarely works and can even cause more problems. Cutting corners usually costs more money in the long run.

 

Ok thanks. I'll get back with what I find