I've been riding my '02 in the woods with an aftermarket 12oz flywheel practically since I got it and never thought much of the whirring noise the bike makes, I just figured that's what a big bore Yamaha sounds like. Now I've recently bought an '01 that I've left stock as a track bike. It has the stock flywheel in it and there is no noise like my '02 makes. Is it possible the weighted FW could be making that noise? I thought it could be the timing chain too but it has a self tensioner right?