2001-2005 Honda TRX250EX Sportrax TRX250EX Factory Service Manual, Page 249Get this manual
REAR DRIVING MECHANISM Remove the oil capRotate the ring gear several times in both directions of
rotationCheck the gear tooth contact pattern through the oil filler holeThe pattern is indicated by the Prussian Blue applied to the pinionContact is normal if the Prussian Blue is transferred to the approximate center of each tooth, but slightly to the heel side and to the flank sideHEELFACE FLANK
DRIVE SIDE
COAST SIDE
If the patterns are not correct, remove and change the pinion shim with one of an alternate thicknessReplace the pinion shim with thicker one if the contact pattern is too high, toward the face Replace the pinion shim with thinner one if he contact pattern is too low, toward the flank