2000 Yamaha YFM400FWA(M) Factory Service workshop Manual, Page 259Get this manual
REAR AXLEFINAL DRIVE GEAR AND DRIVE SHAFT
Final gear lash adjustment 1.Remove: Bearing housing Ring gear shim(s) Ring gear Thrust washer 4
2.Adjust: Gear lash
Adjustment steps: Select suitable shim(s) and thrust washer(s) using the following chartToo little gear lash Reduce shim thicknessToo large gear lash Increase shim thickness If