White smoke?!

[Fatimals]

My friend has a yfz450r and it smokes a little on start up and when you rev it real high he thinks it's the valve seals and that he's gonna need to get his valves re done any thoughts on what it could be let me know. Thanks

[Kimura]

Sometimes it could just be that it's not warmed up..

[Ernie Flabbi]

Value seals. You may also have a worn intake guide.

[pain99]

Sometimes if you don't let it warm up and let the rings warm up and seal against the cylinder when you rev it a bunch it will push oil around the rings and smoke. Does it smoke after its warmed up?