VESPA GT 125 Workshop Manual page 54

Maintenance
- Disconnect the SAS check valve vacuum pipe
from the «T» branch shown in the figure.
- Close the branch using a cap or a pipe portion
with conical cap.
- Connect the Mitivac vacuum pump to the control
pipe and to the SAS valve.
- Start the vacuum up to - 0.6 - 0.8 Bar so as to
close the valve and cut off the SAS system.
Remove the exhaust gas collection Kit closing cap and connect the analyser properly pre-heated.
Check the conditions displayed by the analyser and the engine rpm and adjust the CO value at 3.8 ±
0.7 at 1,650 ± 50 rpm
N.B.
CHECK THAT THE RESULT IS OBTAINED WITH THE GAS VALVE IN THE CLOSEST POSITION.
ALSO CHECK THAT THE CARBURETION ADJUSTMENT IS OBTAINED WITH THE FLOW SCREW
OPEN BY 2 TO 4 TURNS.
IF NOT, CHECK THE FUEL LEVEL ADJUSTMENT IN THE BASIN AND CHECK THE FUEL CIRCUIT.
IN CASE OF UNSTEADY CO, CHECK THE CARBURETTOR CLEANING, THE FEEDING SYSTEM
EFFICIENCY AND THE VACUUM SEALS.
IN CASE OF UNBURNT HYDROCARBONS (HC) > OF 1,000 P.P.M., CHECK THE IGNITION SYS-
TEM, THE TIMING, THE VALVE CLEARANCE AND THE DRAINAGE VALVE SEAL.
Specific tooling
020329Y MityVac vacuum-operated pump
020332Y Digital rev counter
494929Y Exhaust fumes analyser
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Vespa GT 125-200