Please help. I have done extensive work on my recon 250 2002 and cannot stop the white smoke. I have new cylinder, piston, rings head and have checked valve seats guides and have put new valve seals. It still smokes. It smokes excessively at starting and diminishes somewhat after running. I have followed the break in procedures and still have smoke. The last time I took the head off I noticed oil on top of the cylinder. Hope someone will have a suggestion on a fix.

 

maybe one ring is broken or the head gasket is messed up some how
what weight oil do you have in it?
you will have to take it apart to see whats wrong

 

I agree, most likely you have got something wrong on rebuild, rings upside down, a valve seal not seated on the guide. Also possible that the head is cracked and leaking oil from the rockers into cylinder or ports. Check the breather is OK too, a blockage causes pressure in the crankcase which has to come out somewhere, and a breather routed onto the filter in the airbox will drip oil onto the filter, which is then sucked in.