My 06 Bruin has ran flawlessly, since 06... Now it's started smoking at high RPM, Mostly when you let off the gas, and uses a little oil. Dad has one too, that has been rode alot less and it doesn't smoke nearly as bad.
The atv set for around 8 months unused, and now the carb tries to flood out when pointed down hill or uphill.

 

I might also add in, that the breather box keeps filling up with engine oil.... the blow by tube for the head, seems to puke out in there.