I have an 03 SX Viper 700 mountain sled with which I have had some bad luck on the engine. The sled in general has consistently had overheating problems in hardpack snow conditions on the trail. Unfortunately that problem and perhaps a power valve problem have led to some pretty severe damage to the engine for the second time in two seasons. I am now becoming paranoid about even bothering to rebuild this engine as it will blow again. Does anyone have any suggestions as to what engines might be compatible with my chassis? Is a swap of engines a feasible idea especially if I can go to one without the power valves as I have heard that Yamaha only used that engine in 2003 and then swtched away from the design due to problems. I would appreciate any thoughts you can share on these issues. Thanks!!

Your engine probably blew up from not getting enough snow in the raditor that help the engine cooled down on the trails. Do you get the red light on all the time? I have Viper Mountain too and when i ride on hard trails, my light comes on cuz of the engine not getting enough snow coming inside. Every once in a while you should gun the gas alittle bit so the track can pick up some snow or ice and hits the raditor or just shut the engine off for 15 mins. but on your thought. might as well give it a shot and try, it can work. Good luck

Thanks for the input. The heat light came on periodically but could be put off by going off trail into the powder or by keeping the running boards loaded with snow. It never stayed on for more than a few seconds. Not a very covenient way to run a sled but I thought It would save the engine. I guess I was very wrong. Now I need a good way to get the sled back on the trail either with either a different model engine or a like kind replacement. I will keep my eyes and ears open. All help will be appreciated.

No problem. If your going to be riding the trails where its groomed all the time. If you still ride Yamaha, look into getting the Rough Trail, Crosssover, Trail Ver., or Groomed Trail. They wont have the kind of problem your having with the Viper becasue those sled are much lower than the Viper.