Guys, I bought a WR400 a while back and I love it. However it's burning/using oil. I can't see any smoke coming from the exhaust. I've read that it could be valve stems and seals. I would appreciate any information on this. Is it possible that I need to do a complete top end? Replace the cylinder and head? How can I tell what the problem is? Thank you for your time. Fusedbrain.