1997 Yamaha YFM600FWAK ATV Service Manual, Page 186Get this manual
MIDDLE GEAR
3.lnspect: Gear teeth (drive pinion gear) CD Gear teeth (driven pinion gear) Pittinggallingwear 7 Replace
4.lnspect: O-ring Damage 7 Replace Bearings Pittingdamage 7 Replace5.Check: U-joint movement Roughness 7 Replace U-joint
MIDDLE DRIVE AND DRIVEN GEAR SHIM SELECTION
When the drive and driven gear, bearing housing assembly andor crankcase replaced, be sure to adjust the gear shim CD1.Select: Middle drive gear shim CD Middle driven gear shim