1998-2001 Yamaha YFM600FHM Grizzly Factory Service Manual, Page 218Get this manual
MIDDLE GEAR
Where:numeral (usually decimal number) on the bearing housing is either added to or substracted from "18.5")bearing thickness (considered constant)thickness (considered constant)(illnumeral (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" (ill is 90.01 5) Therefore, the shim thickness is 0.47 mm