VESPA 150, Service Station Manual, Page: 52 / 249

Engine
Poor performance
POOR PERFORMANCE
Possible Cause Operation
Air filter blocked or dirty. Remove the sponge, wash with water and car shampoo, soak
with specific oil for foam filter treatment. Press with your hand
without squeezing, allow it to drip dry and refit.
Excessive drive belt wear Check it and replace, if necessary
Lack of compression: parts, cylinder and valves worn Replace the worn parts
Oil level exceeds maximum Check for causes and fill to reach the correct level
Excess of scales in the combustion chamber Descale the cylinder, the piston, the head and the valves
Incorrect timing or worn timing system elements Time the system again or replace the worn parts
Silencer obstructed Replace
Inefficient automatic transmission Check the rollers and the pulley movement, replace the dam-
aged parts and lubricate the movable guide of the driven pulley
with grease.
Wrong valve adjustment Adjust the valve clearance properly
Overheated valves Remove the head and the valves, grind or replace the valves
Valve seat distorted Replace the head unit
Worn cylinder, Worn or broken piston rings Replace the piston cylinder assembly or just the piston rings
Starting difficulties
START-UP PROBLEMS
Possible Cause Operation
Flat battery Check the state of the battery. If it shows signs of sulphation,
replace it and bring the new battery into service by charging it
for not more than ten hours at a current of 1/10 of the capacity
of the battery itself.
Faulty spark plug Replace the spark plug
Incorrect valve sealing or valve adjustment Inspect the head and/or restore the correct clearance
Starter motor and start-up system fault Check starter motor.
Altered fuel characteristics Drain off the fuel no longer up to standard; then, refill
Air filter obstructed or dirty. Remove the sponge, wash with water and car shampoo, soak
with specific oil for foam filter treatment. Press with your hand
without squeezing, allow it to drip dry and refit.
Fuel pump fault Check the pump.
Excessive oil consumption/Exhaust smoke
EXCESSIVE CONSUMPTION
Possible Cause Operation
Wrong valve adjustment Adjust the valve clearance properly
Overheated valves Remove the head and the valves, grind or replace the valves
Misshapen/worn valve seats Replace the head unit
Worn cylinder, Worn or broken piston rings Replace the piston cylinder assembly or piston rings
Worn or broken piston rings or piston rings that have not been
fitted properly
Replace the piston cylinder unit or just the piston rings
Oil leaks from the couplings or from the gaskets Check and replace the gaskets or restore the coupling seal
Worn valve oil seal Replace the valve oil seal
Worn valve guides Check and replace the head unit if required
Troubleshooting
Vespa Primavera125 - 150 i.e. 3Valvole (2013)
TROUBL - 52