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ROYAL ENFIELD WORKSHOP MANUAL
also controls the fuel supply via a connecting pipe
to the right-hand instrument which does not have
a float chamber in unit with it.
It is important that the pilot air screws of both
carburetters are in identical positions, relative to
one another, the same applying to the throttle
valves when seated on their stops. This is essential
for an even smooth tickover and low-speed
running. The speed of the tickover is regulated by
these four adjuster screws. For an instant pick-up,
both throttle valves must commence to rise from
their stops simultaneously, when the twist grip is
rotated. This is obtained by adjusting the twin
control cables. Each main jet needle must be in
the third groove.
Both air slides, operated from a single
handlebar lever, must open and close identically,
as failure to do this may result in one slide not
opening fully, with a resultant loss of power.
It is most important that all of these
adjustments are carried out in a thorough and
careful manner if the maximum power and
smoothness is to be obtained.
The "ears" to be found on the leading edges of
the battery and toolbox lids are to shield the
carburetter air intakes and so prevent misfiring at
maximum revs.
3. Dismantling Carburetter
The construction of the carburetter is clearly
shown in Fig. 3.
If the float chamber floods, first make sure
that there is no dirt on the fuel needle seating.
Owing to the use of a nylon needle and the
leverage ratio between float and needle, flooding
is very unlikely.
PAGE 44
with this type of carburetter unless dirt is present
or, of course, the float is punctured.
If it is necessary to remove the jet block note
that this is withdrawn from the upper end of the
mixing chamber after unscrewing the jet holder.
Be careful not to damage the jet block when re-
moving or refitting it. Note that the large
diameter of the jet block pulls down on to a thin
washer.
A single strand of an inner control cable is
useful for clearing the small passages in the jet
block and care must be taken not to enlarge these
by forcing the wire through them. Compressed air
from a pipe line or a tyre pump is preferable. A
choked main jet should be cleared only by
blowing through it.
4. Causes of High Petrol Consumption
If the petrol consumption is excessive first
look for leaks either from the carburetter, petrol
pipe, petrol tap(s) or tank. If coloured petrol is in
use this will readily indicate the presence of any
small leaks which otherwise might pass unnoticed.
If the petrol system is free from leaks, carefully set
the pilot adjusting screw as described in
Subsection 2 to give the correct mixture when
idling. Running with the pilot adjusting screw too
far in is a common cause of excessive petrol
consumption. If the consumption is still heavy try
the effect of lowering the taper needle in the
throttle slide by one notch. Do not fit a smaller
main jet as this will not affect consumption except
when driving on nearly full throttle and may make
the mixture too weak at large throttle openings,
thus causing overheating. Remember that faults in
other parts of the machine can have a marked
effect on petrol consumption. Examples of this
are binding brakes, chains too tight or out of line
and, in particular, under-inflated tyres.
F4
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