Defects In Operation; Check For Air Leaks; Sticking Of Piston - Triumph SPEED TWIN 1945 Workshop Instruction Manual

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DEFECTS
IN
O P E R A T I O N
When the engine runs erratically, faults other than carburation can be contributory
causes. Before interfering with the carburetter, the following possibilities should
be considered
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Compression-Equal pressure i n both cylinders; check tappet clearances.
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r (b) Moisture condensation (water)-Examine float chamber and H.T. cables.
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(c) Ignition System-Inspect the distributor points, clean and adjust i f necessary.
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Contact breaker and condenser condition is most imponant. Sparking plugs should
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be cleaned and re-gapped (See Technical Data) and pressure tested. Correct timing
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!' i s vital t o good idling. in particular excessive advance and faulty operation of the
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..
automatic mechanism must be recrified.
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(d) Check for air leaks:-
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(i) Between the MANIFOLD and CYLINDER HEAD.
(ii)
Between the MANIFOLD and CARBURETTER.
(iii) Between the T W O HALVES of the CARBURETTER.
(iv)
At
the SUCTION CHAMBER CAP.
If, however, the engine and ignition are found t o be faultless the following points
should be checked on the carburetter:-
:v)
tP
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S T I C K I N G O F P I S T O N
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The symptoms here are either stalling and a refusal of the engine t o run slowly or,
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alternatively, lack of power accompanied by excessive fuel consumption. This
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defect is easily detectable. When the engine is not running the piston should rest
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,
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upon the bridge (28). When raised by the hand through the air intake, the p i s t ~ n
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should drop freely and strike the bridge sharply and distinctly. T o do this the filter
rubber connection must f i r s t be removed.
If it becomes prematurely arrested in i t s downward movement, o r appears unduly
reluctant t o break away from its position of rest on the bridge when an attempt is
made t o raise
it
from this position, the jet should be lowered by means of
its
lever,
and the test repeated.
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If the symptoms persist,
it
can be assumed that either the large diameter of the
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piston is making contact with the bore of the suction chamber, o r the small diameter
w i t h the carburetter body, o r that the piston rod is not sliding freely within
its
bush.
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When, on the other hand, sticking has been eliminated by the act of lowering the jet,
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the indication is that the needle
i s
binding on the jet either due t o
its
being bent o r
t o the latter being out of centre. Normally the needle should never touch the jet
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orifice when correctly assembled.
(if visual evidence clearly indicates needle wear and jet ovality, both should be
renewed).
Rectification should be conducted as follows according t o the diagnosis:-
DIRT OR CONTACT BETWEEN THE PISTON A N D SUCTION CHAMBER, O R
STICKING OF THE PISTON ROD IN ITS BUSH.