Adjusting the Vespa carburetor

Adjusting the Carburetor on the Vespa - Here's How

VESPA - CARBURETOR

The choice of carburetor size has a significant influence on the performance and characteristics of the engine. Sensibly usable carburetor sizes range from 19 mm to 35 mm.

In addition to the experience of other mechanics, there are also formulas or tables to determine the required carburetor size. This is primarily determined by RPM and displacement:

• d = carburetor diameter (mm)
• Vh = displacement volume (liters)
• n = RPM max. power (1/min)
• k = factor (empirical, approx. 0.7 to 0.8 for scooter engines)

VESPA - ADJUSTING THE CARBURETOR

Many engine damages result from poorly tuned engines. Critical are compression, squish band, ignition, and carburetor adjustment.

The correct carburetor setup is not as simple as the ignition timing and cannot be checked as easily. Our Jetting Tips Table helps you find an initial reference point.

SPARK PLUG IMAGE

Modern synthetic oils make interpreting the spark plug image more difficult. After a full-throttle run, however, the plug can be used as a rough indicator.

A grayish/snow-white plug

Too hot combustion - do not continue operating the engine!

A black spark plug

Indicates a too rich setting or too high oil content.