Engine Maintenance and Modification Bradley Artigue

FIAT 124 Spider
Engine Maintenance + Modification
Upon opening of throttles, the diaphragm (50), under the action of cam (53) and lever
(52), injects fuel into primary carburetor throat through duct (54), delivery valve (55) and
nozzle (46).
Spring (51) absorbs quick throttle opening and allows regular feeding from jet (46). Any
excess fuel delivered by accelerating pump, together with pump chamber vapors, is
exhausted into bowl (16) through calibrated orifice (48). Upon closing throttles, lever (52)
sets free the diaphragm (50) which draws in fuel from bowl (16) through ball valve (47),
under the action of spring (49).
Figure 30: ADF Starting
The choke is of semi-automatic type: this means that to insert it when engine is cold, it
is necessary to depress the accelerator pedal completely, then to release it slowly to
normal position.
Once the starting device is inserted, the bimetallic coil (68) — via lever (67), spindle (56),
lever (57) and rod (58) — keeps the choke plate (59) closed. At the same time, the cam
lever (60) will be in the position as shown in Fig. 4 and, by means of lever (25) —
adjustable by screw (61) — it will keep the primary throttle (23) partially open (fast idling).
In these conditions, the nozzle (8) delivers a given amount of mixture which, diluted with
the air controlled by starter plate gape, allows a quick starting of the engine.
After starting, the vacuum set up beneath throttle (23) through duct (64), acts on
diaphragm (65) which being displaced by rod (66) and bush (62) the latter held by the
spring (62) make the lever (67) rotate against the action as the bimetallic coil (68) which,
via spindle (56), lever (57) end rod (58), will partially open the starter plate (59) thus
supplying a mixture strength suitable to allow a normal engine running.
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