VIDEO| Polini talk us through the new casings
We’ve just returned from EICMA in Milan, and amongst all the modern bikes and scooters, there are still tuning houses making new things for our classic scooters.
Here’s the first one we’re going to take a look at. Polini have created this brand spanking new set of large frame Vespa engine casings and they have a few very useful features to set them apart from others on the market.
Main tech features
- Flat reed valve for use with standard type carburettors and autolube
- Racing reed valve as an option for larger carbs
- Crankcases numbered and paired during machining for perfect alignment and maximum flatness
- Optimised fluid dynamics through CFD simulations on transfers for superior performance
- Added strengthening ribs and internal metal, reinforced gearbox area around the axle
- Enlarged ignition side bearing (25x25x15) for better smoothness & durability
- The driveside bearing can be removed externally (fixed in place with a cover)
- M8 hexagonal screws for more rigid assembly (replaces M7)
- Reinforced shock mount and cylinder base
- Relocated gearbox oil fill cap to increase oil capacity
- Clutch cover with an extra labyrinth to increase oil volume
- Provision has been made for an electric start if required
Material
The Polini crankcases are cast in shell moulds from light AI S110 Mg T6 aluminium, thermally treated to ensure maximum mechanical strength, thermal stability, and long-lasting durability.
No gasket
The mating surface between the case halves has been increased to achieve better sealing and stability, even under high thermal expansion. No gasket is required.
Bigger bearings
There are a few well-thought-out features that make the Polini cases stand out. For starters, the driveside bearing and oil seal can be removed without splitting the casings. This makes things much quicker if they need to be replaced. The bearings have also been beefed up to increase their lifespan and performance. They are the only part of these casings that aren’t interchangeable with standard PX items.
More meat
As well as extra gasket faces, additional bracing has been cast into the cases in areas prone to weakness. It’s possible to machine them to fit larger wheels if needed.
More volume
To increase oil volume, the oil filler hole has been relocated higher up the casings, and the clutch cover has been made with an extra labyrinth section.
This engine requires 500ml of gearbox oil (a standard PX engine uses 250ml).
Choice of reed valve
As standard, you can use the Polini cases with their flat reed valve and a standard type Si carburettor – complete with autolube. The engine on show had a Polini Si carb and a large volume airbox fitted. There is an option to fit a larger 28/30mm carb on a dedicated intake manifold and reed valve.
Versions
Two versions of the engine are available, PX125/150 – part number 170.0600 and PX 200 – part number 170.0601
Price and availability
The casings are due to arrive in April 2026. The 125/150 casings will be priced at €719 and the 200 at €818. The clutch covers will arrive in January and cost €148. Keep your eye on Polini or your nearest stockist.
