VESPA ET4 50, Workshop Manual

Page: 35 / 185

Engine
Poor performance
POOR PERFORMANCE
Possible Cause Operation
Air filter clogged or dirty Disassemble, wash sponge with water and shampoo and im-
merse in a mixture of 50% petrol and Selenia Air Filter oil. Let
it drip. Wring out without squeezing it and then refit
Carburettor nozzles clogged or dirty Dismantle, wash with solvent and dry with compressed air
Dirty or faulty vacuum-operated cock Check the filter on the cock, remove the petrol and wash the
tank, if necessary. Replace the cock as a last resource.
Clutch slipping Check the clutch system and/or the bell and replace if neces-
sary
Inefficient automatic transmission Check the rollers and the pulley movement, replace the dam-
aged parts and lubricate the driven pulley moveable guide with
Montblanc Molybdenum Grease
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 encrustations in the combustion chamber Descale the cylinder, the piston, the head and the valves
Timing failure or timing system parts worn Reset timing phase or replace any worn parts (refer to 4-stroke
50 cc engine manual)
Muffler obstructed Replace
Fuel filter on vacuum operated cock blocked Clean the cock filter
Wrong valve adjustment Adjust the valve clearance properly
Valve seat distorted Replace the head assembly
Worn cylinder, Worn or broken piston rings Replace the piston cylinder assembly or just the piston rings
Rear wheel spins at idle
REAR WHEEL
Possible Cause Operation
Idling rpms too high Check the idling speed and, if necessary, adjust the C.O.
Clutch fault Check the spring/friction mass and the clutch bell
Air filter housing not sealed Correctly refit the filter housing and replace it if it is damaged
Purifier-carburettor fitting damaged Replace
Starting difficulties
STARTING PROBLEMS
Possible Cause Operation
Defective spark plug or with incorrect electrode gap Check and if necessary replace the spark plug and the elec-
trode gap
Battery flat Check the state of the battery. If it shows signs of sulphation
replace it and bring the new battery into service charging it for
eight hours at a current of 1/10 of the capacity of the battery
itself
- Engine flooded. Start up keeping the throttle fully open alternating approximate-
ly five seconds of turning it with five seconds still. If however it
does not start, remove the spark plug, the engine over with the
throttle open being careful to keep the cap in contact with the
spark plug and the spark plug grounded but away from its hole.
Refit a dry spark plug and start the vehicle.
Vacuum operated cock failure Check that fuel is adequately supplied through the pipe by ap-
plying a vacuum to the suction pipe
Failing automatic starter on the carburettor Check the electrical wiring and mechanical movement, replace
if necessary.
ET4 50
Troubleshooting
TROUBL - 35