Cylinder -POLINI 75 ccm Racing- Vespa V50 (1st series - cylinder base Ø=56,8mm)

Polini 75cc racing cylinder for Vespa V50 first series

Early Vespa V50 models, colloquially known as the V50 first series, have a different design in many details to the later V50 models.

The chassis numbers belong to the early models:

• V5A1*1001* to *92877
• V5SA1*1001* to *15325*

The first series models are easily recognizable by their very small engine cover (just under a hand's width high) as well as their 3-speed gearbox and small 9-inch tyres. The engine of these early 50cc Vespa models, in conjunction with a long primary reduction ratio of 3.72 selected ex works and a large jump from gear 2 to gear 3, is too tired for today's everyday use. The long gear ratio virtually predestined the engines for an increase in displacement by means of a larger cylinder. However, the early V50s have a smaller cylinder base bore in the engine housing, so the readily available cylinders of the later models do not fit here.

To avoid dismantling the engine, we offer a suitably machined cylinder. This replaces the old cylinder 1:1 and we chose the Polini 75cc in the racing version. With a very nice rev range and an output of over 4 hp, it is exactly the right candidate to pull the V50's gearbox, which is a little too long. The wide rev range clearly helps to overcome the long jump from second to third gear.

In our cylinder kit you will find an M6 sheet metal nut as an accessory, this is used to create the screw connection point between the fan wheel cover and the cooling cover and can simply be placed on the fan wheel cover. This is necessary because the fixing points on the V50 1° are oriented differently.

Polini specifies an ignition timing of 17° for this cylinder. If you are still using a contact ignition on the engine, you can use the test lamp to set the ignition timing to 1.4 mm before TDC. Depending on the exhaust and whether a racing shaft is installed in your engine, you should adjust the main jet in the carburetor accordingly. In the installation instructions, Polini recommends a main jet of 66-68 for the SHB 16 carburetor, but we cannot confirm this value. Experience has shown that the carburetor should be equipped with a jetting of 74-84.