Workshop Manual

REG. CODE
1-5302-509
MODEL N°
50778
DATE OF ISSUE
10.06.99
REVISION 00
DATE
10.06.99
ENDORSED
COMPILER TECO/ATI
58
FUELLING CIRCUIT
XI
144
Carburetor with variant to keep the engine idling when cold
Components:
1 T union
2 Accelerated idling adjuster screw
3 Pressure hole
4 Thermovalve
5 Pneumatic actuator on the carburetor
6 Calibrated hole
7 Not in the drawing - Plant 2193-113 (see fig. 164 on page 73)
Operating principle
Thermovalve 4, which guarantees regulation of the on-off type in the air circuit, is installed on the water pump support to
adjust to the temperature of the aluminium.
The thermovalve is then connected by tubes in the following way:
a) union parallel to its axis, with union 1 free on the actuator plenum (obligatory route B-B)
b) union slanting, with union after the throttle of carburetor 3 (obligatory route A-A).
There is a T union 1 with calibrated hole 6 to allow the idling actuator to be released in the connection between the plenum
and thermovalve.
Make sure that the hole is free to prevent the engine from remaining accelerated when hot, and check that the reduction is
installed to prevent the engine from accelerating when idling and cold.
To ensure the device operates in the correct way, the system also has an electronic module to handle the ignition phase:
compared to the original one, which gave an increasing timing to to 3000 r/min, the modified module has a constant 11°
timing up to 2000 r/min in closed throttle conditions.
This allows an optimum adjustment of the air device when hot.
The actuator consists of a diaphragm which, controlled by the vacuum, allows the throttle valve to open and the idling speed
to be consequently corrected.
This means that once the engine has started and the starter has been disengaged, the idling speed (initially around 1050 -
there is a certain delay in the system) then stabilizes at around 1200 to 1300 r/min.
From the moment in which the system reaches its running speed, with gradual heating of the engine, the idling rate rises to
about 1600 to 1700 r/min before the solenoid valve cuts out the device.
Adjusting the device
To adjust the idling speed, connect the actuator straight on to the carburetor (on the union after the throttle, see fig. 144),
bypassing the thermovalve.
After having warmed up the engine, adjust regulation screw 2 on the upper part of the actuator, see fig. 144, to obtain a speed
of about 1700 r/min (tighten the screw to decrease the supplementary opening of the throttle and lower the rotation speed of
the engine, and vice versa).
Now re-connect the tubes on the thermovalve and on the carburetor, then adjust the idling speed of the engine to around 1100
speed by means of the idling speed screw.