2004 Official factory service manual for Yamaha YFZ450S ATV Quad., Page 76Get this manual
ADJUSTING THE VALVE CLEARANCE EAS00048
ADJUSTING THE VALVE CLEARANCE The following procedure applies to all of the valvesNOTE: Valve clearance adjustment should be made on cold engine, at room temperature When the valve clearance is to be measured or adjusted, the piston must be at the Top Dead Center (TDC) on the compression stroke1