2004 Official factory service manual for Yamaha YFZ450S ATV Quad., Page 112Get this manual
ADJUSTING THE DRIVE CHAIN SLACK CHECKING THE STEERING SYSTEM CAUTION:
Excessive chain slack will overload the engine and other vital parts; keep the slack within the specified limitsdIf the chain slack cannot be adjusted, replace the sprockets and drive chain as seteTighten the hub nuts and locknutsHub nut 85 Nm (8.5 kg, 61 ft lb) Locknut (chain puller) 16 Nm (1.6 kg, 11 ft lb)