I took my bike to the local yamaha dealer because it was running like crap. They said all I need is probably a valve adjustment. When they took it apart they discovered that my cam chain was stretched and my bike was out of time. They said it wouldn't cost to much to fix because my valve clearance was still fine and nothing got bent when it went out of time. Two days later they phoned me back and said that the drive gear that is attached to the crank shaft was damaged and that it would cost 1800.00 to fix. My questions Can the drive gear be changed or does the whole crank assembly have to be replaced? Can I service the drive gear by just taking off the crank case cover? Is this something I could handle myself? How much should this cost to fix?