Just finish my 103 big bore and SE 255 cam stock head, i start the bike on wednesday for 2 or 3 minutes everything was ok so i stop the motor, yesterday i start the bike again and a white smoke came out from the the right side muffler and the smoke don't stop i check for a leak and found oil around the flange so i change the gasket and torque the bolt start the bike again and same problem.my oil level is ok
What can be wrong !!! valve ,oil ring ...

 

Could be a valve seal. If that doesnt fix it then you could have the rings in wrong OR your piston doesnt match the hole.

I had the same problem once, oil would literally drip out of my exhaust port. It was a mis match between jug and piston, my own stupid fault.

 

Had a buddy do a top end on an evo last year, same problem. It was a broken ring.

 

yep sounds like a ring bummer

 

Found the problem, my mistake :-( the second compression ring was install upside down so the ring does'nt scrape the oil down.

 

oops.. you will be smarter next time ..... The good news it wasnt a broken ring as that can mess the cylinder all up.... Dont want that ..