Yamaha YFM250XL(C) Service Manual page 197

MIDDLE GEAR SERVICE
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Middle gear shims selection steps:
Shim selection Å
When the crankcase and/or the drive pin-
ion gear are replaced, be sure to adjust
the drive pinion gear shim Å.
To find drive pinion gear shim thickness
"A" use following formula:
Drive pinion gear shim thickness:
a= The stamped number on the drive pin-
ion gear is either added to or sub-
stracted from "42".
b= The stamped number on the crankcase
is added to from "41".
NOTE:
All stamped numbers are in hundredths of
a mm.
Example:
1) If the drive pinion gear is stamped
"+02"
.... a = 42 + 0.02 = 42.02
2) If the crankcase is stamped "45"
..... b is = 41 + 0.45 = 41.45
3) Therefore, shim thickness Å is,
Å = 42.02 - 41.45 = 0.57 mm
4) Shim sizes are supplied in the following
thickness:
Thickness (mm)
Because shims can only be selected in 0.05
mm increments, round off hundredths digit
and select appropriate shim(s).
Hundredths
0, 1, 2
3, 4, 5, 6, 7
8, 9
6 - 11
DRIV
Å = a – b
Drive pinion gear
shim
0.15 0.40
0.20 0.50
0.30
Round value
0
5
10
6