37-1-614 Page 51
FIGURE 7-28 – SMALLEST MINUS READING
FIGURE 7-29 – SMALLEST PLUS READING
The final check to be made for running clearances
is dividing the interlobe clearance of the rotors to
prevent metal-to-metal contact. This is referred to as “TIMING OF ROTORS” and is accomplished in the
following steps.
28. Install the gear (7) on the hub, (FIGURE 7-28, page 51), which is a slip fit. If gear teeth were
marked at disassembly, line up these marks. New gears are not marked and should be
positioned so tapped holes in the hub are centered with holes in the gear to allow radial
movement on the gear for timing. Tighten the “Nylok” screws (49) against the flat washers (50)
(always use new washers) just tight enough to allow the gear to slip radially on the hub. Mount
an indicator and button bracket as shown in
FIGURE 7-28
, page 51. In order to accurately follow
the next four steps in timing, the indicator must be mounted in a clockwise position from the
bracket. The gear has a 3/8-16 tapped hole for indicator support. When the indicator is mounted,
hold the gear from rotating and with a wrench in one of the hub retainer screws, move the shaft in
a clockwise direction until all slack is taken out of the gears and rotors to give a metal-to-metal
contact. To prepare for the first reading, set the indicator at zero.
29.
FINDING SMALLEST MINUS READING
– (FIGURE 7-29, page 51). Hold the gear under
clockwise pressure to maintain metal-to-metal contact. Rotate the shaft counterclockwise
two
complete revolutions
with a wrench. (Do not rotate by moving the gear.) If at any time the
indicator hand moves to the plus side, reset at zero, and again rotate two complete revolutions.
Notice the place of the smallest reading (This is the smallest number of thousandths from zero,
not the smallest figure on the indicator dial). Continue rotation until the smallest reading is again
reached and reset the indicator at zero. This is the closest clearance of rotors in this direction of
rotation. If the indicator pointer flutters at any time during rotation, check for burrs or dirt on the
rotors or gear teeth.
30.
FINDING SMALLEST PLUS READING
– (FIGURE 7-30). Hold the gear under counterclockwise
pressure to take up all slack, and rotate the rotor clockwise
two complete revolutions
with a
wrench. Note the place of the smallest plus reading, and continue rotation until the smallest
reading is again reached and stop. This is the point of minimum interlobe clearance.
