[hunter]

My son's 99 XC500 blows back oil into the air box. Enough that after a 75 mile ride, oil [a couple of spoons ] leaks onto the floor.
The reeds apear OK, no leaks from the oil lines, everything else is dry. Would appreciate some help or ideas.

 

[Jethro790]

Does the machine blow excessive smoke? Even when warmed up?

 

[hunter]

Exessive smoke

No machine does not smoke excessively.
Other info. that may help-- pistons look OK from intake,exhaust,& spark plug holes. Compression is 121psi both cylinders.
Work done approx. 1000 miles ago-- Rebored .020 " over with new Wisco pistons,& Boison reeds.
Hope this will help!