The dirt/dual sport miles are easy on the engine but the 200 hours as a snowbike are full open, full load most of the time. Upon tear down the rings had .017 ring end gap (service limit is .004). I thought I would need to change the piston but it is well withen service limit and the cyl is like new. Changed the valve guide seals for good measure. It is suprising how well these engines hold up. I use Mobil 1 15-50 engine oil and a good motorcycle trany oil and change the engine oil often.