Motorcycle Repair: lots of white smoke from exhaust, header pipes, valve seals

Question
what causes white smoke to pour out of the exhaust as i give it gas,and while at idle.smoke is thick and takes a good 15 minutes to stop

Answer
Sounds like you have oil in the header pipes.  Could be bad rings or generally worn bores if it keeps smoking.  If it does finally stop, perhaps it is just getting in there from the valve train, which means your valve seals are bad.  It would help to know what bike it is.  Jan