Short Description
The automatic choke units used on Vespa motor scooters are both basically the same and both work in the same way. Remember that the choke defaults to being ON so it is unlikely that a cold starting problem is due to a malfunctioning choke.
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Content
OPERATION
• The choke unit has a plunger that is pushed down to close off a hole at the bottom of a drilling in the carburetor.
• A wax pellet is heated electrically and expands, as it heats up it pushes out the plunger. As the wax warms the electrical resistance measured across it increases until it becomes open circuit. In most circumstances the choke will then remain off purely by the heat of the engine.
• The time taken for the choke to turn off is controlled only by the rate at which the wax expands. The ambient temperature will affect the time taken for the choke to turn off.
• The choke is activated once the engine has started and not when the ignition is turned on.
Vespa ET2 50cc engine.
These motor scooters have headlights that are run from 12 volts AC. 12 volts AC is used to operate the choke. AC can only be supplied when the engine is running so the choke cannot begin to turn off until the engine is running.
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