1997 Yamaha YFM600FWAK ATV Service Manual, Page 187Get this manual
MIDDLE GEAR Where:
a numeral (usually decimal number) on the bearing housing is either added to or substracted from "18.5"C =: bearing thickness (considered constant)thickness (considered constant)=: numeral (usually decimal number) on the right crankcase specifies thickness of "90"Example: 1) If the bearing housing is marked "+02" is 18.52 2) is 16 3) is 55 4) If the crankcase (right) is marked "90.01" is 90.01 5) Therefore, the shim thickness is 0.47 mm=