Carburetter Pistons.
Sluggish and uneven running may be caused by sticking carburetter pistons.
When the engine is thoroughly warm, remove the air cleaner and connections,
switch off the engine and then check that the carburetter pistons fall freely when
lifted and released. If any of the pistons stick, the cause may be dirt in the suction
chamber or an incorrectly centred jet. To examine a suction chamber, remove its
three securing screws and lift off the cover, when the chamber and piston can be
cleaned with a non-fluffy rag. Do not use metal polish or emery cloth. If when the
piston is replaced
it
does not fall freely,
it
is probable that the jet is not correctly
centred or the jet needle is bent. In the latter case needle should be replaced.
To centre the jet, remove the nut cap, release the large hexagon screw half a
turn or so and then screw up the jet as far as it will go, noting the number of turns.
This procedure will centre the jet on
the needle and the large hexagon screw can
now be tightened. Finally, release the jet the same numbzr of turns as were needed
to screw it up fully.
Slow Running.
When the idling setting is correct, the carburetters will operate properly at
all speeds. The two adjustments on each carburetter effecting slow running are the
throttle stop screw and the jet adjustment screw. The jet adjustment screws weaken
the mixture when screwed up and enrich
it
when screwed down. When these
screws are correctly adjusted, lifting any of the pistons with a thin blade will slow
the engine down. If the lifting of the piston makes the engine go faster, it indicates
that the carburetter setting is too rich and must therefore be weakened. At the
same time
it
may be necessary to enrich the other two carburetters until a good
balance is obtained.
Starter Carburetter.
The only adjuster is the idling hexagon screw through which the needle passes.
When the engine is hot and the starter carburetter is switched on, the screw should
be adjusted upwards as far as possible without uneven running of the engine. If
next time a cold start is attempted, the engine starts and then stops, the adjusting
screw should be released another third of a turn.
Air Cleaner.
The three cleaner elements should be removed and cleaned every
5,000
miles.
To do this remove the air cleaner by unscrewing the three bolts which secure the
cover plate and the three elements to the back plate. Immerse the elements in
petrol and wash thoroughly.
Allow to dry and then dip in clean engine oil. Shake
out any surplus oil and reassemble.
When carrying out the above operation
it
is necessary to disconnect the rubber
Servo connection. Care must be taken to prevent dirt from entering the system
whilst the pipe is disconnected.
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