2001-2003 Honda TRX500FA Factory Service Manual, Page 308Get this manual
REAR DRIVING MECHANISM Replace the pinion gear shim with thinner one jf the contact pattern is too low, toward the flankThe pattern ill shift about 0.5-1.0 mm (0.02-0.04 inwhen the thickness of the shim is changed by 0.12 mm (0.005 in )
NOTE: Nine different thickness shims (f ro toare available in thickness intervals of 0.06 mm (0.002 in)
PINION GEAR SHIMS: (thinnest): 1.64 mm (0.064 in(st andard): 2.00 mm (0.079 in) (t hickest): 2.18 mm (0.086 in )
For pinion shim replacement, see page 18-11