(No need to remove nut.)
Lever off sprocket until it is loose on the taper of the shaft. (Use stout
screw-driver or old type tyre lever.)
Turn over engine till both valves are closed.
Insert rod through sparking plug hole, feel piston by rocking engine
forwards or backwards till it is felt the piston is at the top of its stroke
with both valves closed,
Mark rod flush with top face of sparking plug hole. Remove rod and
measure ½" above the flush mark and record position on rod-
Turn the front plate of the automatic unit with the fingers and thumb
to its limit of movement and insert a wood wedge to hold the control in
the fully advanced position.
Replace rod in sparking plug hole.
Slightly rotate engine BACKWARDS until upper mark on rod is flush
with top face of sparking plug hole. (To rotate engine, engage top gear
and turn back wheel by hand.) Rotate sprocket on magneto armature
shaft, in anti-clockwise direction (as seen from sprocket end of magneto),
till the contact breaker points are just about to separate. (To find the
exact moment for the commencement of the point separation, place a
piece of tissue paper between the points and turn the armature shaft
(by the sprocket on it) until the paper is just released, and no more, by
a gentle pull.)
Tighten nut on camshaft and ensure engine, and/or magneto shaft, does
not move in doing so.
Re-check the setting which must be ½" before top dead centre. (With
the ignition fully advanced.)
Do not omit to remove the wood wedge securing the automatic unit
in the fully advanced position before refitting the chain cover.
Replace
Rocker box side cover, magneto side cover, magneto chain case cover,
sparking plug and sparking plug wire.
VALVE TIMING
Standard Heavyweight Models
Taken with valve .001" off its seat
Inlet valve timing.
Inlet valve opens 36° before top dead centre—350 c.c. models,
Inlet valve opens 18° before top dead centre—500 c.c. models.
Inlet valve closes 51° after bottom dead centre—350 c.c. models.
Inlet valve closes 69° after bottom dead centre—500 c.c. models.
Exhaust valve timing.
Exhaust valve opens 50° before bottom dead centre—All models.
Exhaust valve closes 30° after top dead centre—All models.
Camshaft timing marks.
Use mark 1 for exhaust cam—all touring models.
Use mark 2 for inlet cam—500 c.c. touring and competition models.
Use mark 2 for exhaust cam—all competition models.
Use mark 3 for inlet cam—350 c.c. touring models.
When checking the valve timing the tappet clearances must be set to
34
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