Incredibly, it's now 111 years since the Esposizione Internazionale Ciclo Motociclo e Accessori (EICMA) motorcycle show was first held in Milan. Since then it's grown to be one of the world’s largest motorcycle shows and in 2024 around 600,000 visitors flocked to see displays by 770 companies from 45 countries representing 2,163 brands. As has become traditional, this year’s show was held in the first week of November and looks like being another record breaking event.
Although the event is famous as an opportunity for major manufacturers to unveil their latest models (see our modern blog for Vespa news) a wide range of parts for classic scooters are also on show. Probably the best news that PX owners have received in a while was Polini’s unveiling of high specification, but still affordable, engine cases for large frame Vespas.
Turning weakness into strength
It’s been a long time since we’ve been able to regularly offer original PX casings, large or small block, from stock as Piaggio deleted them from their spares catalogue some time ago. Not only is it getting harder to find unmolested casings at a sensible price, we all know that the original designs are a compromise. Although perfectly crafted for mass assembly on a production line, the design creates inherent problems for anyone trying to repair an engine and although perfectly capable of dealing with (almost!) any punishment a standard set up can throw at them, the increased horsepower offered by modern tuning kits has exposed structural weaknesses in the castings.
Having considered these problems, Polini has proudly unveiled their own casings, designed to both make maintenance easier and create a platform capable of absorbing increased power.
The casings, which are available in both 125/150 and 200 variants offer the following advantages over Piaggio's original design:
Revolutionary Fuel system
The transition from the traditional rotary valve system to a flat reed valve system allows for:
- Elimination of carburetion issues related to the sealing of the original valve
- Improved engine delivery and overall performance
- The installation of a racing reed valve pack with a 28/30 mm carburettor
(Alternatively to the flat reed, a racing reed valve pack with a peak design, without a mixer, is available, along with a dedicated intake for 28/30 carburettors.)
Mechanical and structural innovations
Crankcases are numbered and paired during machining, ensuring:
- Perfect alignment of bearings
- Maximum flatness of the mating surfaces
Completely redesigned swing-arm geometry with:
- FEM analysis for structural reinforcement
- Added ribs and internal over-metal to accommodate larger wheels
- Reinforced gearbox area around the wheel spindle
Advanced technical details
- Modification of the assembly to prevent the clutch side oil seal from coming off
- Ground steel flanges for bearing support on the clutch side
- Enlarged ignition side bearing (25x52x15) for better smoothness and durability
- M8 hexagonal screws for a more rigid assembly, replacing the traditional M7 through bolts
- Reinforced shock absorber mounts and cylinder base
- Possibility to install the electric start
- Relocated gearbox oil filler cap to increase lubrication capacity
Material Quality
Polini crankcases are made from light aluminium alloy Al Si10 Mg T6, cast in shell moulds, and treated thermally to ensure:
- Maximum mechanical strength
- Thermal stability
- Long-lasting durability
The elimination of the central gasket and the increase of the mating surface between the halves-cases also ensure better sealing and stability, even under high thermal expansion
Advance ordering
We’re expecting the cases in stock sometime around April 2026, with indicated retail prices being approximately £794 (Inc VAT) for the 125/150 casing £825 (Inc VAT) for the 200cc variant. The clutch cover will be available at the same time and cost around £130.
However, if you're serious about your engine build and want to be amongst the first to own one of these cases, subscribe to our newsletter now as we’ll soon be announcing a very special pre-order deal.
