250R engine problems??

[Pro1200]

So I took down my top end thinking that is what the problem is, but my piston and cylinder look pretty good...My machine shop guy said it might be the crank seal? How can i tell if mines is good??

When I last rode my R friday...the idle went from 1500 to 500rpm, felt like it was losing power each time i rode it, and it bogged out every time i tried to give it power, now its also easy to kick start, and i did a compression test and it lost a bit of compression, Also every time i tried pulling the clutch for powerband or downshifting I still dint gain anymore power. I just switched to a 38mm carb as well. I doubt its re jetting issues because the compression dropped

Any idea what it is?
:confused:

Thanks again guys

[trx310R#24]

Originally posted by Pro1200
[B]My machine shop guy said it might be the crank seal? How can i tell if mines is good??B]

leak down test.. and it sounds like a head gasket... if your piston is good and you lost comp id check that.

[Pro1200]

my head gasket wasn't leaking though

[86 Quad R]

did you perform a WOT plug chop on it after switching over to the 38mm carb. there is a remote chance that the jetting was on the lean side and could have very well damaged the rings, piston and bore.