Amal Carburetor; Operation Of Carburetor Parts; Throttle Stop Screw; Pilot Air Screw - Triumph SPEED TWIN 1945 Workshop Instruction Manual

Amal Carburetter
AMAL CARBURETTER
(Models 5T. TR5, TI00 & TttO)
The
AMAL
needle jet carburetter i s fitted t o all the above mentioned models and,
unltxs the machine is t o be used for some special purpose, we strongly recommend
that the settings are not interfered with. The settings are arrived at after careful
experiment and It is unlikely that a different setting will improve the fuel con-
sumption, o r increase the maximum power output. Alternative settings are however
listed for the models TI00 & TI10 when the
air f i l t e r is disconnected.
During the early life of the machine
it
is advisable t o remove the float bowl and
clean
it
out occasionally t o prevent the jets becoming blocked.
A
common cause of
erratic running at low speeds, explosions i n the silencers and poor pick-up when
accelerating
i s
a CHOKED SLOW RUNNING ORlFlCE
IN
THE JET BLOCK. T o
remedy this fault, the carburetter mixing chamber must be completely dismantled
and the jet block withdrawn t o gain access t o the orifice. To clear, push a thin
strand of wire through the hole t o dislodge any foreign matter. Wash the jet block
i n petrol and dry off w i t h pressure air t o ensure that
all
passage ways are perfectly
clear.
O P E R A T I O N
OF
CARBURETTER PARTS
T h r o t t l e Stop Screw. This screw should be set t o open the throttle sufficiently
t o keep the engine running
a t
a low tick over when the twistgrip i s shut off.
P i l o t Air Screw. To set the idling mixture, this screw should be set in or our t o
enrich o r weaken, normal number of turns is about 2f. The screw controls the
suction on the pilot petrol jet by metering the amount of air which mixes with the
petrol.
N e e d l e and N e e d l e Jet.
A
tapered needle
is
attached t o the throttle and either
allows more o r
less
petrol t o pass through the needle jet as the throttle i s opened
o r closed throughout the range, trcept when idling o r nearly full throttle.
The taper needle position in relation t o the throttle opening can be set according t o
the mixture required by fixing
it
t o the throttle with the needle clip spring in a
certain groove, thus either raising o r lowering
it.
Raising the needle enriches the
mixture; lowering
it
weakens the mixture at throttle openings from a quarter t o
three quarters open. Machines are delivered from the factory with the needle in
the fourth notch from the top, and the needle should be lowered t o the middle notch
after 1,000 miles (1,500 Kms.).
T h r o t t l e Valve Cut-Away. The atmospheric side of the throttle i s cut away t o
influence the depression on the main fuel supply and thus gives a means
d
tuning
between the pilot and needle j e t range of throttle opening. The amount of cut-away
i s
recorded by a nunlber marked on the throttle viz.,
613
means throttle type 6 with
No. 3 cut-away; larger cut-aways. say
4
and 5 give weaker mixture and
2
and 1 richer
mixtures.