Correct me if I'm wrong. Once upon a time Ski Doo sleds all had Bosch plugs from the factory. My only two listings apply to a 470 cc motor in the MX model sled in 1994 -1995. This info came from a NGK listing which calls for BR9ES regular NGK or BR9EIX (iridium) NGK. Both plugs call for a .016 gap!
Most of the other motor sizes call for a .020 gap.