CARBURATION
So long as the engine continues to run satisfactorily the carburetter is best left alone,
particularly by the inexperienced rider. The setting employed is suitable for a very
wide range of climatic conditions, and it is highly improbable that the rider will need
to modify it in any way. If however, it is felt that the conditions under which the
machine is operated might permit of a slightly more economical setting this can be
provided by the fitting of a smaller main jet (A) Fig. 6, or by lowering the jet needle
(B) one notch. The former alteration will supply a slightly weaker mixture
throughout the entire range of throttle opening, whereas an alteration to the jet needle
position has little or no effect on the full throttle setting. Conversely, the fitting of a
larger main jet enriches the mixture throughout the entire range, while raising the jet
needle a notch has a similar effect on intermediate throttle openings only. It is
emphasized, however, that no alteration to the setting should be made except for
special requirements, and only then on expert advice.
ALL MODELS
S
PECIAL
N
OTE
:— New riders especially are advised to study the action of the
strangler and to treat this device with respect. It should only be used
MOMENTARILY
when starting from cold and even then only when necessary. Immediately the engine
fires it should be opened. This point is of special importance in the event of difficult
starting, possibly due to some other circumstance such as a defective sparking plug,
for repeated operation of the kickstarter with the strangler closed results in the
accumulation of liquid petrol in the crankcase and when this occurs, starting is quite
impossible until it is drained away by the removal of the crankcase drain plug, which
is the smaller of the two plugs under the crankcase.
Air Cleaner
This is built into the carburetter intake bell and, as it is of the oil-dip type, it requires
to be dismantled and cleaned periodically, say, every thousand miles (1,500 km.). To
do this, release the clip bolt, and take the bell off. Soak it thoroughly in petrol, allow
it to dry, and then submerge in light engine oil for a few minutes. Then take out,
allow the surplus oil to drain off, wipe the exterior, and reassemble.
Carburetter Strangler
This is built into the air intake “bell” of the carburetter, and consists of a perforated
plate which when rotated covers or uncovers similar perforations in the bell, thus
varying the amount of air admitted to the carburetter. When the strangler is “closed”
(i.e., brought into operation) by raising the small lever on the right-hand side, this
closes the perforations, thus reducing the air admitted to the carburetter to a minimum
and providing in consequence a very rich mixture. The strangler should at all times
be kept open except when starting from cold.
TRANSMISSION
Front Chain
The front chain runs on short fixed centres and adjustment for tension is neither
required nor provided.
This chain will run for many thousands of miles before examination is required.
This operation involves the removal of the primary chain cover (Fig. 7), after the
kickstarter and gearchange pedals, both of which are mounted on splines and locked
by pinch bolts (B) and (C) respectively, have been removed, together with the five
securing screws (D). The normal up and down play on the front chain is up to
⅜
in.
(1 cm.) and the maximum permissible, indicating that the chain is unduly worn and
requires replacement, is about ¾ in. (2 cm.).
17
