I have a 2005 Rubicon Foreman 500 - motor was rebuilt not long ago & it has no blow by on rings. It does not smoke and has plenty of compression. The valvetrain seems a bit noisy to me but other than that nothing remarkable I can think of. This bike only pushes racecars, no mudding, rivers, sand, etc. So it pretty much lives a spoiled life compared to most... Recently the bike got doggy, really bad... looked in airbox and there must be a half qt of oil in there. Dumped it out, replaced filter & its doing it again - what is causing this?