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Motorcycle Repair/vespa scooter ccarb


setting piolet jet on a cv carb Can you describe the best way to set  the piolet jet on a 50 cc vespa.thanks

Hi ronryman,

Warm up the engine before any tuning is done.

Turn the pilot screw in until the engine falters and then turn the screw out
until you get the fastest engine speed while still idling.

Then turn the screw in slightly, try to get the highest engine idle speed
that is still smooth.

If the engine is idling its highest speed at  0-1 turns out this means the pilot jet setting is lean and a larger pilot jet may help.
If the engine idles its highest speed  over 2 turns out this means the pilot jet setting is rich and a smaller pilot jet may help.

This theory applies when your pilot adjustment screw is near the rear of the carb as this
is a pilot air screw. A pilot screw nearer the engine is a pilot fuel screw and meters the fuel more so than air.
The above theory is reversed on these fuel type pilot screws.

The pilot or slow jet also has some small emulsion holes in it that may get plugged up so a clean
carb is always essential to good tuning.


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Wayne S.


Licensed Motorcycle Mechanic, Knowledge of motorcycles from 1960 up, Japanese, British and most other brand motorcycle repairs.


Worked for Yamaha, Honda, Suzuki, Kawasaki British: Triumph, Norton, BSA Other: Most Scooters and Mo-Peds

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