Thrush Aircraft S2R-R1340 Maintenance Manual page 74

THRUSH AIRCRAFT, INC – MODEL S2R-R1340
A. Remove one spark plug from each
cylinder, and rotate the propeller
shaft until No. 1 piston is at the
beginning of the compression stroke.
B. Install PWA-4142 (or equivalent)
indicator in the front spark plug hole
of No. 1 cylinder (use pivot arm "A"
with hook end down).
C. Attach the red wires of PWA-2417
(or equivalent)
breaker points of the magneto and
ground the black wire to the engine.
D. Align the cap of the indicator so the
slide slot lines up with the vertical
axis of the cylinder and the scale is
at the right of the slot. Push the slide
pointer up close to the pivot arm.
E. Turn the propeller shaft in the normal
direction of rotation until the pivot
arm pushes the slide pointer to its
farthest point.
F. Turn the
approximately 90 degrees opposite
normal rotation to return the pivot
arm to the top of the slot. Adjust the
scale so that the zero degree mark
on the scale
reference mark on the slide pointer.
G. Move the slide pointer up to align
with the 25 degree mark on the
scale. Turn the propeller shaft until
the picot arm just contacts the slide,
at which time the lower light in the
PWA-4142 indicator flashes on. The
piston is now 25 degrees before top
center.
H. At this point the lights of the PWA-
2147 indicator
simultaneously, indicating that the
points are just opening. Check the
alignment of the timing marks with a
straightedge.
correct "E" gap.
are 1/32-inch on either side of the
timing marks. If the timing is correct,
no further action
however, if the timing of either
magneto is incorrect, proceed with
the remaining checks.
4-4
AIRCRAFT MAINTENANCE MANUAL
indicator to the
propeller shaft
aligns with the
should flash on
This will give the
Permissible limits
is necessary;
I. Remove the bolts that attach the
incorrectly timed magneto to its
mounting pad
magneto away sufficiently to turn the
rubber drive coupling.
J. To advance the timing, turn the
rubber coupling one or two notches
in a counter-clockwise
Recheck timing.
K. To retard the timing, turn the rubber
coupling in a clockwise direction.
Recheck timing.
*NOTE*
The rubber coupling has 19
notches on one side, and 20
notches on the opposite side,
allowing for
adjustment by rotating one
notch at a time.
L. After the timing has been corrected,
slide the magneto back into position,
install and lockwire the magneto
retaining bolts.
If the magneto is not properly timed,
adjust the breaker points as indicated by
the following steps:
A. With the indicator still connected and
the straightedge aligned, loosen the
contact bracket screws and turn the
eccentric adjusting screw until the
indicator light
indicating that the points are just
opening. Tighten the contact bracket
screws.
B. Remove one spark plug from each
cylinder. Turn propeller shaft until
No. 1 piston is at the beginning of
the compression stroke. Install
PWA-4142 (or equivalent) indicator
in the front spark plug hole of No. 1
cylinder (use pivot arm "A" with hook
end down).
C. Align the cap of the indicator so that
the slide slot lines up with the vertical
axis of the cylinder and the pivot arm
is at the top of the slot. Push the
slide pointer up close to pivot arm.
and move the
direction.
a very fine
just flashes on,
Effective: 01/01/2008