2008 Yamaha Raptor 250SE / 250SE2 Factory Service Manual, Page 127Get this manual
CYLINDER HEAD
bRemove the screwdriver and slowly release the timing chain tensioner rodcMake sure that the timing chain tensioner rod comes out of the timing chain tensioner housing smoothlyIf there is rough movement, replace the timing chain tensioner3Check: Cap bolt Copper washer Spring One-way cam Timing chain tensioner rod DamagewearReplace the defective part(s)