2006-2014 Honda FourTrax ATV TRX250 EX TRX250X Service Manual, Page 138Get this manual
CYLINDER HEADVALVECAMSHAFT Turn the crankshaft counterclockwise and align the punch mark ("250"side) on the cam sprocket with the index mark on the crankcase
Push in the tensioner shaft while pressing the stopper block to retract tensioner lifter and secure it with pin