TOHATSU BFT250A Service Manual page 493

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HOW TO SELECT SHIM COMBINATION
To obtain 0.90 mm (0.035 in) of shim thickness,
combine one gear shim A, one gear shim C, and one
gear shim D, or combine four gear shim A and one gear
shim D.
FORWARD BEVEL GEAR SHIM
Assemble the outer race [1] and the inner race [2] of a
new taper bearing (60 x 100 x 30 mm), and turn the
outer race two or three turns.
Place the bearing assembly on a flat surface [3] with its
tapered side facing down.
Press the outer race down over the inner race and
measure the bearing height (F) [4] from the outer race
end to the inner race end using a regular vernier caliper
[5] as shown, and record the measurement.
Calculate the tolerance using the measurement F
obtained in the previous step and the following formula.
Formula: Tolerance = F – 30.5
Example:
When measurement (F) from the outer race end to the
inner race end is 30.55 mm (1.203 in):
Tolerance = 30.55 – 30.5 = 0.05
The tolerance is 0.05 mm (0.002 in).
Remove the trim tab from the gear case (page 16-8).
Cross reference the engagement mark [1] located on
the trim tab installation part of the gear case [2] and the
tolerance calculated in the previous step, and refer to
the forward bevel gear shim selection table to
determine the required thickness of the shim (Sf).
Forward bevel gear shim selection table
Refer to page 16-38 for information on how to read the
shim selection table and shim combination.
Select the shims from the forward bevel gear shims of
different thickness to obtain the required thickness (Sf)
by combining the shims.
Shim type table
Install the trim tab on the gear case (page 16-9).
After shim selection, inspect the forward bevel gear
backlash (page 16-41).
Calculation value
0 – +0.05 –
+0.05 +0.10
1 0.40 0.35
2 0.35 0.30
3 0.30 0.25
4 0.25 0.20
5 0.20 0.15
6 0.15 0.10
Shim type Thickness
Shim A 0.10 mm
Shim B 0.15 mm
Shim C 0.30 mm
Shim D 0.50 mm
GEAR CASE (STANDARD ROTATION)
[1]
[3]
Unit: mm
+0.10 – +0.15 –
+0.15 +0.20
0.30 0.25
0.25 0.20
0.20 0.15
0.15 0.10
0.10 –
– –
[5]
[2]
[1] [2]
16-39
[4]