I just picked up a 99 yz400 and I have a few questions for you guys. I have read some posts of people having to change their timing chain and I asked the guy that sold me the bike and said you never have to replace those. Is this true? Also, the guy has the idle set pretty high because he rides in the woods and didn't want to stall, I tried moving the idle screw to turn it down, but it seems like the screw is stuck and will not move clockwise nor counterclockwise, whats up with this? Thanks guys, any other tips on the bike would be great.