VALVE TIMING, Standard models
taken wit h 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.
(See page 86 for particulars of special timing disc graduated in degrees.)
Camshaft timing marks
Use mark 1 for exhaust cam—all models.
Use mark 2 for inlet cam 500 c.c. touring models.
and all competition models.
Use mark 3 for inlet cam 350 c.c. touring models only.
When checking the valve timing the tappet clearances must be set to ·014 inch so that
the tappets may be well clear of the quietening curves of the camshafts.
The timing gears are marked to facilitate their replacement.
To re-set the valve timing, by using the marks on the gears, proceed as
follows :—
Turn over the engine till the mark on the small timing pinion is in line with the
centre of the inlet (rear) camshaft bush. Insert the inlet camshaft so that the No. 2
or No. 3 mark on it is in mesh with the mark on the small timing pinion, according to
model.
Rotate the engine in a forward direction till the mark on the small timing pinion
is in line with the centre of the exhaust (front) camshaft bush. Insert the exhaust
camshaft so that the No. 1 mark on it is in mesh with the mark on the small timing
pinion.
VALVE TIMING, Trials models
Inlet opens 26° before top dead centre.
Inlet closes 53° after bottom dead centre.
Exhaust opens 64° before bottom dead centre.
Exhaust closes 25° after top dead centre.
taken with 0·016" tappet clearance and with the valve 0·001" off its seat.
F—S
Illustration 10
31
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