Ask for all service bills, if the seller says he did all service himself ask him how he did this (valve adjustment) ask him to show you the tools he used for it. He may well have the tools but if he doesn't and can't tell you off the top of his head he's not being truthful.
Check the oil and see what color it is, if it's dark brown or black stay away, he may have just changed it for the sale but some people are lazy and won't.
Ride it more then around the block, if it seems to slip (trans) you nay have an issue with the CVT. Look for exhaust color, if any blue, black, your burning oil.
Top speed indicated on my peoples200 is 60-62 MPH and people say mine is slow(er) then theirs, if yours doesn't reach that mark you may have a problem. The eng should sound calm and comfortable up to around 40-45 mph, if the bike seems stressed you may have a problem. 50MPH and higher revs you'll hear the bike sounding stressed or not calm sounding.
Look for obvious wear items like brake wear, also drop marks incase he had an accident and laid the bike down, mirrors will have marks or have been replaced, plastic will have cracks, scuffs or been replaced. If all the panels don't exactly match color wise that maybe the case.
Look at his other cars/bikes if a private seller, it tells you how he cares for things. If the garage is a mess, his repair record may suffer too.
