Remove the bolt securing the automatic timing control to the cam
wheel shaft. Fit a 024328 withdrawal bolt in place of the fixing bolt
removed which should be lightly tightened. A sharp blow on the end of
the withdrawal bolt will dislodge the unit from the shaft.
Do not disturb the contact breaker cam.
Setting the ignition timing. Maximum advance 500 c.c. also 350 c.c. with
engine number before 41575 is ½" or 39 deg. (12.7 mm). 350 c.c. after
41575. Y" or 34 deg. (8.73 mm). With the A.T.C. retarded use 8" for ½"
or x" in place of Y".
To set the timing, have available a stiff wheel spoke or similar object
5½" long.
Remove H.T. cable and sparking plug.
Remove automatic timing control as already described.
Remove the rocker box side cover.
Turn engine so that both valves are closed (inlet valve opens then
closes) then engage top gear.
Insert timing rod through sparking plug hole, feel piston by rocking
engine forwards or backwards by turning the rear wheel until it can be
felt that the piston is at the extreme top of its stroke with both valves
closed.
Refer to Fig. 6. and fit automatic advance control, with the gap formed
by the two bob weights in line with the two tapped holes, used to secure
contact breaker plate. It should be noted that the peak of the cam, or
narrowest part, when correctly positioned is approximately at 12 o'clock.
Press the unit firmly on to the shaft that drives it and give the end a
sharp tap before re-fitting the fixing bolt. Insert a wood wedge between
bob weights to fully separate if fully advanced method is used.
Take up the timing rod, check piston position in case the engine has
moved. Hold the timing rod as vertically as possible through the sparking
plug hole, verify piston is at the top of the stroke. Make a mark on the
timing rod flush with the top face of the sparking plug hole, then withdraw
the rod.
If the fully advanced method is used make a further mark on the timing
rod exactly ½" ABOVE the previous mark.
With the A.T.C. retarded mate the second mark as shown in the figures
given.
Put the timing rod back through the sparking plug hole and by moving
the rear wheel turn the engine BACKWARDS until the highest of the
two marks on the timing rod is flush with the top face of the sparking
plug hole, dependant on the timing method used.
Fit the contact breaker plate with the capacitor at 3 o'clock, lightly
tighten the fixing screws. The exact position of contact point separation
is best determined by inserting a strip of cigarette paper between the
contact points and moving the plate in a clockwise direction until the
paper can be pulled away freely.
If a wedge is used to fully advance the unit, scribe a pencil line on the
contact breaker plate and a similar Line on the plate housing, both lines
in register. Remove the contact breaker plate, take away the wedge and
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