Last year on a warmer day{about minus 5} it took out the clutch side piston. Yesterday, about the same temp it took out the other side. I pulled it apart and the jug is pretty scored up, the clutch side piston has some small scoring on it as well but the jug looks and feels fine. It has 140 main's, I was thinking when I put it back together I should stick 150's in to be safe.. Good idea? Any one have problems like this with there's? Thanks!

What do the plugs look like? Does it consume oil properly? For what it's worth my wifes '02 mxz 380f uses 185 mains, it too has the mikuni vm30s, but I think the needles are different. I've seen these engines take alot of abuse, we've ran them above 40°F all day before. Running in warmer temps you should actually be richer, so leaning out doesn't make sense. How's the fan belt tension? It may be slipping, causing overheating.

my 2000 380 went 5000k so far and never burped ever, not on hot days either. too bad

Could the seals in the crankcase be bad? Maybe you should have a leakdown test done on the sled. If jetting is stock, I would suspect that something else is causing your problem.

Yes, it sounds like a leak down test should be done.

for what its worth: I BOUGHT A NEW 97 TOURING E 380, IT HAS HAD NUMEROUS BRUTAL BEATINGS, IT HAS BEEN HIT BY DEER AND TREES, BUT IT HAS ALWAYS RUN FLAWLESSLY. I HAVE ALWAYS RUN HI TEST FUEL AND SKI DOO OIL IN IT, AND AGREE WITH THE OTHERS ABOUT FANBELT, JETS, LEAKDOWN TEST.

Thanks for the advice guys. Cory9

i loved my 380. that thing just kept going and going. rings let go at 13,000 km's tho. always rode it to the bar. :D