2000 Yamaha YFM400FWA(M) Factory Service workshop Manual, Page 252Get this manual
REAR AXLEFINAL DRIVE GEAR AND DRIVE SHAFT
FINAL DRIVE PINION GEAR AND RING GEAR POSITIONING When the final drive pinion gear, ring gear, final gear case andor ring gear bearing housing are replaced, be sure to adjust the positions of the final drive pinion gear and ring gear using the shim(s)
Final drive pinion gear shim selection 1.Select: Final drive pinion gear shim(s) 1