1986-1987 Honda TRX350 FourTrax 4X4, 1987-1989 TRX350D Foreman 4X4 Service Manual, Page 158Get this manual
CRANKCASECRANKSHAFT TRANSMISSION Replace the drive gear adjustment shim with thicker one if the contact is too low The pattern win shift about 1.0 mm (0.04 in) when the thick ness of the shim is changed by 0.10 mm (0 04 in)(1) TOO LOW :
OUTPUT DRIVE GEAR ADJUSTMENT SHIM: A: 0.40 mm (0.016 in) B: 0.45 mm (0.018 in) C: 0.50 mm (0.020 in) Standard D: 0.55 mm (0.022 in) E: 0.60 mm (0.024 in)
Check the backlash (See page 11-14)