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throttle must be fully closed. If not, adjust the pedal and throttle
by means of end piece 10 at front rod 1 end.
Secure the end of throttle linkage cable 3 so that with knob 5
pulled, the choke is fully closed, while with knob 5 pushed in - fully
open.
Engine idle adjustment. This is to be done via idle mixture
adjustment screw 2 (Fig.2-91) and throttle stop screw 1. Cap 4 is
provided for adjustment screw 2. Remove the cap to access the
screw.
Idle adjustment is done on the warm engine (coolant to be at
85-90°ë), after the valve gaps and ignition timing are correctly
adjusted, the choke should be wide open.
Using throttle stop screw 1, set the crankshaft speed within
750-800 rpm.
Using idle mixture adjustment screw 2, set the content of car-
bon monoxide (CO) in exhaust emissions at maximum 1.5 % with
throttle stop screw 1 at the preset position as above (CO level is
for 20°ë and 101.3 ÍP‡ (760 mm Hg).
Reset the crankshaft speed to 750-800 rpm by means of
throttle stop screw 1.
When applicable, restore CO level to the maximum 1.5 %.
On completion, sharply depress and release the throttle pedal
- check to see the engine speeds up without any gasps and does
not stall at lower rpm. Should the engine stops, use throttle stop
screw 1 to increase the engine speed to 750-800 rpm.
Refit new plastic cap 4 to idle mixture adjustment screw 2.
Checking the secondary barrel locking linkage. Turn the
choke lever anticlockwise to fully close the choke. Next, turn spin-
dle 19 lever (Fig.2-89) to wide open primary throttle 23; sec-
ondary throttle 24 must remain closed
Turn the choke lever fully clockwise, turn throttle lever 19 to
wide open the throttle. If the secondary throttle fails to open, elim-
inate the fault. The fault can be caused by seized secondary lock
lever 20 or disconnected lock lever spring 21.
Exhaust gas recirculation system
The vehicle is fitted with the exhaust gas recirculation (EGR)
system which comprises thermo-vacuum switch 2 (Fig.2-92) and
EGR valve 5 with the relevant port and recirculation tube 6 in
intake pipe 3.
When coolant is over 40-48°ë, the thermo-vacuum switch
triggers to build-up vacuum in the EGR valve; the valve opens to
reintroduce small amount of exhaust gas from exhaust manifold
4 into the intake pipe and inside the engine.
Checking EGR system operation. Depress the throttle lever
and smoothly raise the engine speed to 2500-3000 rpm. At
coolant temperature of 30-38°ë EGR valve 5 must be closed,
while at coolant temperature of 40-48°ë it must be open, which
can be evident through the EGR valve rod upward travel. If the
Fig.2-92. Exhaust gas recirculation:
1 - carburettor; 2 - thermo-vacuum switch of EGR valve; 3 - intake pipe;
4 - exhaust manifold; 5 - EGR valve; 6 - recirculation tube
EGR valve does not open, check the proper operation of the EGR
valve and thermo-vacuum switch 2.
To check the EGR valve, disconnect the thermo-vacuum
switch. Using manual vacuum pump, build up vacuum in the EGR
valve diaphragm cavity. The EGR valve must be closed at 9.3
kP‡ (70-75 mm Hg). With vacuum level over 59.9 kPa (450-455
mm Hg) the EGR valve must be fully open, which is checked
through a sharp vacuum removal - the EGR valve closes with a
distinct click. In both cases no air leaks are allowed within 5 sec-
onds.
To check thermo-vacuum switch 2, disconnect the hose and
EGR valve 5. Using manual vacuum pump, build up vacuum of
13.3 kP‡ (100±5 mm Hg) to the thermo-vacuum switch. At
coolant temperature maximum 30-38°ë no vacuum leaks are
allowed (thermo-vacuum switch is closed). At coolant tempera-
ture below 40-48°ë there should be no vacuum (thermo-vacuum
switch is open).
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