Engine case -POLINI reed valve intake- Vespa PX125/150 Elestart and Motovespa PX125/150 Iris, 125/150 CL
The completely redesigned POLINI engine cases with diaphragm intake for Vespa PX125/150 Elestart and the Spanish Motovespa models PX125 Iris (99M), PX150 Iris (75M), 125 CL (9CL) and 150 CL (9NC) combine modern flow technology with the robustness of classic large-frame engines. They are designed as a performance-oriented replacement for the original Piaggio or Motovespa engine housing and form a stable basis for powerful street and racing setups.
For PX125/150 Elestart
For Motovespa Iris/CL
Diaphragm intake 28/30 mm
CFD optimized flow
Intake concept and carburetor mount
Instead of the classic rotary valve intake, POLINI uses a newly designed reed valve intake for these engine cases. The flat diaphragm channel replaces the rotary valve-dependent control and thus eliminates all problems that can arise from worn or damaged intake sealing surfaces.
Changeover from the standard rotary valve to a modern diaphragm system with flat lamella.
Significantly more stable mixture formation and cleaner response over the entire usable speed range.
Designed for racing reed valve blocks with 28/30 millimeter carburetors - ideal for performance-oriented setups on PX125/150 Elestart and Motovespa Iris/CL.
Alternatively available: Racing reed valve block in pyramid shape without separate lubrication, with its own intake manifold for 28/30 millimeters.
Despite the new intake concept, the housings remain fully compatible with the original Vespa and Motovespa components in their periphery. This makes it easier to convert from the standard engine housing and allows existing add-on parts to continue to be used, provided they match the desired performance level.
Mechanical and structural optimizations
POLINI has not simply copied the motor housing, but has redesigned it in many respects. The two halves of the housing are numbered as a pair at the factory and machined together. This means that the bearings and sealing surfaces are precisely aligned with each other, which noticeably improves running smoothness and durability.
Housing halves are manufactured and numbered as a pair for a perfect bearing fit and plane-parallel contact surfaces.
The crankcase and transfer ports are designed for optimum gas flow using CFD simulation.
The swing arm has been redesigned and reinforced using FEM analysis; additional ribs and material reserves allow the use of wider rear wheels.
The area around the rear axle stub is reinforced in the gearbox housing to cope with the higher torque of more powerful engines.
Bearings, seals and screw connections
Typical weak points of the original PX and Motovespa housings have also been addressed. On the clutch side, the design has been modified so that the radial sealing ring can no longer move out of its seat unnoticed. A precisely machined steel flange provides additional support for the crankshaft bearing.
Modified design on the clutch side to reliably prevent the radial shaft seal from migrating out.
Ground steel flanges as a support for the crankshaft bearing on the clutch side, for high dimensional stability.
Larger crankshaft bearing on the ignition side (25 x 52 x 15 millimetres) for smoother running and longer service life.
M8 hexagon head bolts are used instead of the classic continuous M7 bolts, which increases the rigidity of the entire housing assembly.
The central housing seal is no longer required; instead, the two halves of the housing lie directly on top of each other with an enlarged contact surface. In conjunction with a suitable sealant, this results in a very stable and largely temperature-resistant connection - a clear advantage over the tired aluminum housings of the first series.
Chassis connection and peripherals
In addition to pure engine performance, POLINI also keeps an eye on the peripherals. The attachment points of the shock absorber and cylinder base have been specifically reinforced to provide a solid basis for sporty suspension set-ups and higher continuous performance.
Reinforced shock absorber connection, suitable for more rigidly tuned suspensions and touring set-ups.
Reinforced cylinder contact surface for high clamping forces and stable sealing conditions for tuning cylinders.
Preparation for electric starter - ideal for PX125/150 Elestart and correspondingly equipped Motovespa models.
The gear oil filler neck has been repositioned to increase the oil quantity and thus the lubrication reserve.
Material and manufacturing quality
The motor housings are cast from a high-quality aluminium alloy Al Si10 Mg T6 using the permanent mould process, followed by heat treatment to optimize the mechanical properties.
Light metal alloy Al Si10 Mg T6 for high strength with moderate weight.
Heat treatment for stable material properties even at high continuous temperatures.
Enlarged sealing surfaces and reinforced areas at all critical points.
Field of application
The POLINI engine cases for Vespa PX125/150 Elestart and the corresponding Motovespa models PX125/PX150 Iris and 125/150 CL are designed as a platform for demanding road and racing engines. Whether a powerful touring engine with reed valve intake or an uncompromising racing setup - the combination of modern intake concept, optimized flow and reinforced structure offers ample reserves for setups far beyond the standard performance without sacrificing the Vespa characteristics.
FAQ: POLINI engine cases PX125/150 Elestart and Motovespa Iris/CL
Frequently asked questions
How does the POLINI housing differ from the original PX125/150 or Motovespa Iris/CL engine housing?
In addition to the change to reed valve intake, the flow, bearing and structure have been completely revised. The housings are more stable, offer space for wider tires, larger bearings and an optimized oil supply, but remain compatible with most Vespa or Motovespa components in the periphery.
Do I necessarily have to use a 28/30 millimetre carburettor?
The housing is designed for diaphragm systems of this size, as this is where the potential is best exploited. Smaller carburettors are technically possible, but do not fully exploit the advantages of the system.
What about separate lubrication?
Variants with separate lubrication are available for the flat diaphragm intake. There is also a pyramid diaphragm block without an oil pump with its own intake manifold. Depending on the set-up, either mixed or separate lubrication can be used.
What is the advantage of the larger crankshaft bearing on the ignition side?
The larger bearing improves running smoothness and increases the service life at high engine speeds and with powerful cylinders. Particularly in combination with heavy fan wheels or speed orgies, this is a plus for operational reliability.
For whom is it worth switching to POLINI engine cases?
The use of POLINI engine cases is particularly interesting for new builds and engines whose performance target is significantly higher than standard. If you have a modern reed valve intake, powerful cylinders and suitable exhaust systems, you get a housing base that is not a limiting factor in the setup.
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