36
08
Disassembly and Reassembly
Operator’s Manual 2009 Rev B p/n 2009
20. The gear hub should now be cool enough
to assemble the gear shells. The dowel pins
should be in the hub. Transfer if necessary.
Reinstall the timing shim and assemble the
shells to their proper hubs, aligning hubs and
shell match marks. Install drive gear first (right-
hand helix), and then align the match marks on
the teeth and assemble driven gear (left-hand
helix).
The six cap screws that were in the drive
gear are too long without the drive shaft.
Temporarily use the six cap screws from the
driven gear. Use three in each gear (every
other hole).
Adjusting Interlobe Clearance
21. The timing gears are made up of two pieces.
The outer gear shells are fastened to the inner
hubs with six cap screws and are located with
two dowel pins. By adding shims between
a gear shell and the inner hub, the gear is
moved axially relative to the inner hub which
is mounted on the rotor shaft. Being a helical
gear, it rotates as it is moved out and the rotor
turns, changing the clearances between rotor
lobes. Adding 0.012 in. (0.30 mm) shim
thickness will change the rotor lobe clearance
by 0.003 in. (0.076 mm).
The timing shim is formed from a number of
0.003 in. (0.076 mm) shims, which have been
laminated together. Easily peel them apart as
necessary.
Use feeler gauges to check the clearance at
AA (right-hand reading) and BB (left-hand
reading) (
see Figure 8-2
). The clearances
should be adjusted so they are as equal
between all lobes as possible, usually between
0.003 to 0.004 in. (0.076 to 0.10 mm). For best
results, use feeler gauges no larger than
0.006 in. (0.15 mm).
A
B
B
B
A
B
A
A
A
A
B
A
B
B
A
B
LONG FEELER GAUGE
LONG FEELER GAUGE
RECORD A-A
READING HERE
RECORD A-A
READING HERE
RECORD B-B
READING HERE
3 LOBE
2 LOBE
RECORD B-B
READING HERE
B
B
B
B
B
B
B
B
B
B
B
B
A
A
A
A
A
A
A
A
A
A
A
A
DRIVE
DRIVEN
DRIVE
DRIVEN
Figure 8-2 – Checking Rotor Interlobe Clearance
Example:
If AA reading is 0.030 in. (0.76
mm) and BB reading is 0.022 in. (0.56 mm),
removing 0.016 in. (0.40 mm) shim will change
the readings one-quarter of this amount or
0.004 in. (0.10 mm). AA reading will drop
to 0.026 in. (0.66 mm) and BB reading will
increase to 0.026 in. (0.66 mm).
To determine the amount of shim to add or
remove from the driven gear, simply subtract
the two readings 0.030 in. (0.76 mm - 0.022 in.
(0.55 mm) = 0.008 in. (0.21 mm) and double
the result 0.008 in. (0.21 mm) × 2 = 0.016 in.
(0.42 mm).
To determine whether to add or remove this
amount, the following rule will always apply: If
the right-hand reading (AA) is greater than the
left-hand reading (BB), remove this amount.
If the right-hand reading (AA) is greater
than the left-hand reading (BB), remove this
amount. If the right-hand reading (AA) is less
than the left-hand reading (BB), then add this
amount.
