My son has a 1981 Enticer. There was a problem with the carb and we had the local Yamaha dealer rebuild it with new seals and whatever else (and new fuel filter too). Used it a few days and it worked great. Then, while on the trail, the engine quit when the throttle was released. Ever since then we can start it no problem but after a minute or less it dies out. Go back a couple hours later and it starts great, then dies. Today I tried something different. Once started I kept the RPM's up just a little (back of snowmobile was raised up) and the snowmobile kept running and running... until I released the throttle. Then it quit and wouldn't start. Done this twice now. I could take it back to the dealer, but we already put so much into the first repair. Anyone have a suggestion?
Kind of sounds like the idle speed is too low,but that would'nt be a intermittent problem,maybe next time it kill's and does'nt start pull a plug and check for spark,sometimes electrical problems can be intermittent. 
maybe sucked some more gunk out of a dirty gas tank? remove the carbs and clean/inspect themtdd77 said:Kind of sounds like the idle speed is too low,but that would'nt be a intermittent problem,maybe next time it kill's and does'nt start pull a plug and check for spark,sometimes electrical problems can be intermittent.