2004 Official factory service manual for Yamaha YFZ450S ATV Quad., Page 78Get this manual
ADJUSTING THE VALVE CLEARANCE 6Adjust: valve clearance
aRemove the valve lifter and the valve pad with valve lapper 3Valve lapper 90890-04101 NOTE: Cover the timing chain opening with rag to prevent the valve pad from falling into the crankcase Make note of the position of each valve lifter and valve pad so that they can be installed in the correct placeMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM