VESPA 664787 Service Station Manual page 40

Troubleshooting
Possible Cause
Altered fuel characteristics
Faulty spark plug
Intake joint cracked or with a bad seal
Purifier-carburettor fitting damaged
Excessive oil consumption/Exhaust smoke
EXCESSIVE OIL CONSUMPTION/SMOKEY EXHAUST
Possible Cause
Excess of encrustations in the combustion chamber
Engine tends to cut-off at full throttle
Possible Cause
Maximum nozzle dirty - lean mixture
Dirty carburettor
Water in the carburettor
Air filter dirty
Defective floating valve
Tank breather hole obstructed
Engine tends to cut-off at idle
Possible Cause
Minimum nozzle dirty
Starter that stays open
Reed valve does not close
Wrong idling adjustment
Spark plug defective or faulty
Excessive exhaust noise
Possible Cause
Secondary metal air pipe deteriorated
Good condition of the missing secondary air circuit components
TROUBL - 40
spark plug and the spark plug grounded but away from its hole.
Drain off the fuel no longer up to standard; then, refill
Remove the encrustation, restore the plug gap or replace being
sure to use the types of spark plug recommended at all times.
Bear in mind that many problems engines have, derive from
Replace intake joint and check for correct sealing on the head
ENGINE STOP FULL THROTTLE
Wash the nozzle with solvent and dry with compressed air
Wash the carburettor with solvent and dry with compressed air
Empty the tank through the appropriate bleed nipple.
Check the proper sliding of the float and the functioning of the
ENGINE STOP IDLING
Wash the nozzle with solvent and dry with compressed air
Check: electric wiring, circuit continuity, mechanical sliding and
Replace the spark plug with one with the specified degree and
INCREASED NOISINESS
Check there are no leaks on the hoses on the crankcase and
the housing, check that there is a cap with filter and it is correctly
Check the individual components and the piping, check the
precision of the fitting. Replace the damaged components
Vespa S 50 2T
Operation
Refit a dry spark plug and start the vehicle.
the use of the wrong spark plug
Replace
Operation
Remove the encrustations
Operation
Clean or replace
valve
Restore the proper tank aeration
Operation
power supply
Check / replace the reed pack
Adequately adjust the engine idle speed
check the plug gap
Operation
fitted to the transmission cover