My 15 ride old '02 426 coughs, sputters, backfires and carbon fouls plugs. It runs but barely. Initially believed to be carburation trouble, I tried on from a friends bike. Then also the CDI, coil, and fuel. All to no avail. What else is left? I can't pull the stator from the bike i'm getting test parts from. Any suggestions? Isn't a carbon fouled plug and indication of week spark? The bike seems to run best when it is completely cold until it gets to temp. Then it's all down hill. I am going to double check the carb, cdi and coil on the "parts bike". Please help!