Motorcycles, Snowmobiles, Go-Carts, ATV's and Golf Carts - Snowmobe over heats?

I have a 1991 skidoo formula mx I put a new thermostat and water pump is working but when i take it out on the snow it still over heats if i take the radiator cap off it blows bubbles and then cools down waht can i do?

Hello ralphluv, got your email and I had read this post a day or so ago. As you can see I live in Mississippi and need you to define something for me......SNOW......Just kidding really but I have zero experience with snowmobiles. If you would post what kind of engine is on it I may be able to help with the overheating....Mike

Its a 463cc engine rotax thanks you guys didnt get any of that snow that hit the south? lol but let me know what you can do thanks

Thanks for getting to me The problem started last year actually and This year i rode it and the same problem happened but it happened after awhile of usage so the thermostat was changed and the water pump seems to be pumping it but when i open the cap and let it sit it cools down but when i put it on and hit the throttle it over heats quick i tryed to bleed it but it still bubbles. I tryed it with the thermostat out and still the same result kind of stuck here thanks please get back

i was just reading your post and up in northern maine we have quite a bit of snow for sledding. I dont know about ski-doos but yahmahas and polarisis have heat exchangers on them and if you have studs in the track once and a while one will come out and poke right through. It sounds like its probably the head gasket but before you spend a lot it might be worth cheacking that is even if ski-doos have them.