I gotta get mine running reliably again...... I rode it one day, then the next day it started backfiring when it warmed up. I think it is the ignition or something electrical. I only run racing fuel in it, and it starts easily from cold, even at 20F. She is rideable cold, but after a minute or so, she starts backfiring off idle. Since it starts and runs, and I run high quality fuel in it, I'd bet it isn't carburetion, but you never know, I guess.