Cylinder kit 75cc Polini Racing modified for Vespa V50 1st series
Now available in the shop: Cylinder Vespa V50 first series 75cc Polini Racing
The early Vespa V50 models, colloquially known as the V50 first series, surprise their owners in some details compared to the widespread, later V50 models.
The early models include, for example, the chassis numbers V5A1 * 1001 * to * 92877 and V5SA1 * 1001 * to * 15325 *
Whether it is the front wheel suspension, the fastening of the rear brake anchor plate with M6 studs, the 3-speed gearbox, the 9 inch tires or the short wheelbase, the V50 models of the first generation are special in many details.
This is also the case when it comes to increasing the performance of the prime mover.
The first V1,2 engines put their drivers at the disposal of a little more than a horse, 50 HP in numbers. This is paired with a reasonably long translated primary of 3.72 and a miserable jump from gear 2 to gear 3 doesn't exactly make these engines into real sprinters.
So what could be more obvious than giving the engine a boost with a new, more powerful cylinder kit.
Here, however, the next surprise awaits. The early V50s have a smaller cylinder base bore in the engine housing - this probably dates from the time when the engine was used as a starter engine for Piaggio aircraft. As a result, the current cylinders do not match.
The motor would have to be completely dismantled in order to properly spindle the cylinder base bore.
In order to avoid this effort, we have machined cylinders appropriately. So you can install the cylinder directly.
Our choice fell on that Polini 75cc in the racing version. With a very nice speed range and an output of over 4HP, it is exactly the right candidate to pull the slightly too long gear of the V50. The wide speed range clearly helps to overcome the rather long jump from second to third gear.
The cylinder base is turned to fit ...
and the fastening point for the fan wheel cover and cooling hood shortened to match.
You will find one as an accessory in our cylinder kit Sheet metal nut M6, this serves the screwing point between Flywheel and Cooling hood and can simply be plugged onto the fan wheel cover for this purpose. This is necessary because the fastening points on the V50 are oriented 1 ° differently.
Polini specifies an ignition point of 17 ° for this cylinder. If you are still using contact ignition on the engine, you can use the test lamp to set the ignition point to 1,4mm before TDC.
Depending on the exhaust and whether one Racing wave is built into your engine, you should have the Main jet adjust accordingly in the carburetor. In the installation instructions, Polini recommends a main jet of 16-66 for the SHB 68 carburetor. However, we cannot confirm this value in this way. Experience has shown that the carburettor should be equipped with a 74-84 jet.
Matching carburetor kits
and a short 3rd gear think.
The racing crankshaft enables the engine to develop a higher torque and the short 3rd gear ensures a better connection when shifting from gear 2 to gear 3.
With such a powerful engine, you can enjoy the summer on your V50 even better.