Crankshaft -MAZZUCCHELLI bell shape (reed valve type)- 60mm stroke, con rod 110mm, gudgeon pin Ø16mm – Vespa PX200

Description

Crankshaft -MAZZUCCHELLI 60mm stroke, membrane (bell shaft)- Vespa PX200

The PX engine offers both advantages and disadvantages due to its crank cheek controlled intake. In case of an uncompromising tuning, unfortunately the disadvantages of positioning the intake directly above the crankshaft outweigh the advantages.

In order to be able to feed the largest possible amount of mixture into the engine, which is necessary for high performance, even at high rpm, it was started early on to replace the original rotary vane control with a self-controlling diaphragm valve system.
It is not the type of intake control that makes the increased performance possible, but only the larger intake surface that is now available by the now possible milling of the engine casing.

One disadvantage remains, however, the rotating crankshaft in the gas flow.

To make a maximum possible cross section available, which is useful for carburettors above 32mm, a new type of shaft was designed:

The so-called bell shaft (or mushroom shaft), whereby the new shape of the crankshaft was used as the name giver.

The bell shaft is the logical consequence of the two specifications:

• maximum flow cross-section
• maximum stability
• perfect balancing

The shaft has no loss of stability whatsoever compared to a conventionally shaped shaft, despite its unusual shape for Vespa drivers. If you have ever looked at a Ducati crankshaft, you may have guessed that this design is not only well thought out but also useful for a high performance engine.

In combination with an increased stroke of 3mm, this results in a crankshaft that is perfectly suited to the demands of an extremely powerful PX engine.

In combination with a large diaphragm intake manifold and a carburetor from 35mm to 38mm, an engine with the right cylinder / exhaust selection can easily deliver more than 35hp to the rear wheel.

Naturally, you can also build beautiful touring engines with such a bell shaft. The advantage is then here in a large speed range and the better torque curve already in the speed cellar by the longer stroke, or the larger displacement.
The very low-vibration run is there only the ‘slim’ on top of it…

Made by the traditional manufacturer Mazzucchelli from Italy.

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