Install three new plugs then start and warm up the sled as described by everyone else here. Do not touch the throttle until the motor is nice and warmed up.... Probably 5 minutes or more. Then report back. DO NOT TEAR INTO THE CARBS UNTIL YOUVE TRIED THE NEW PLUGS........PLEASE!
if the sled was running great, and then suddenly started running bad when u started it cold....almost guarenteid its still a fouled plug problem.
