2008 Yamaha Raptor 250SE / 250SE2 Factory Service Manual, Page 96Get 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 limitseIf the chain slack cannot be adjusted, replace the sprockets and drive chain as setfTighten the rear axle pinch bolts 21 Nm (2.1 mkg, 15 ftlb)