Blown main seal? help!

[j.Lawson]

My buddy has a 98 cr 125r. Today while riding at st. joe it just all the sudden blew smoke everywhere and started to sputter and lose all power. He shut it off, I put it in nuetral and pushed the kick down. It seems to move smoothly, nothing unusual about the piston, connecting rod, crankshaft- and it will start and run. It's just blowing oil and lots of smoke out and sputtering horribly. I think maybe his main seal blew and the oil from the case is entering the cylinder and choking it out? does this sound right? thanks alot.

[SYKO]

possibly... you wil have to do a compression test to see if its leaking out at the seals

[jason 32]

syko - a compression test will not work-
you would need to do a leak down test- this takes different tools-

if it is leaking at the oil side i dont think you need to split the cases to replace it-
the stater side will blow after fixing it --( this is usually what would happen - all the pressure will be on the old seal) so - you might want to spend the 10 bucks ,and do bolth-- also change the water pump seal- it will be worth the little time while your at it

ALSO-- it might be from the center case gasket -letting oil in from there-
i always seal that gasket with sealer-indian head - or gaskasinch-- not yamabond - havent had any problems

[j.Lawson]

Yeah, we havnt had a chance to look into it yet, as Iv thought about it, it could be a number of things, I even thought maybe the head gasket, or possibly cracked cylinder into a water jacket? I dont know, I'll be the one tearing it apart but I dont know about fixing it. I put a knew crank and top end in it last year for him for free. that was about the biggest thing iv ever done..lol. thanks for the reply's.