Crankshaft -MAZZUCCHELLI Racing (rotary valve) K2D 60mm stroke- Vespa PX125, PX150

Preview: Crankshaft -MAZZUCCHELLI Racing (rotary valve) K2D 60mm stroke- Vespa PX125, PX150

Description

Sport crankshaft from Mazuchelli with 60mm stroke (+3mm compared to series).

Mazuchelli now also manufactures its K2D rotary vane crankshafts from the same material that has been used for years for the solid cheek shafts. Mazuchelli advertises with the old material designation K2D which, according to current standards, corresponds to the alloy 18CrNiMo5. Material analyses could not confirm this, but the alloy used is still significantly tougher and harder than the 36CrMn5 alloy normally used by Mazuchelli. Due to the higher core strength, it is possible to achieve a higher press dimension at the crank pin, an important criterion for the torsional resistance of crankshafts. The twisting of the crank webs is one of the biggest problems in tuned PX engines due to a design flaw of Piaggio (the crank webs are too narrow). An increase of the torsional resistance by a better base material is therefore obligatory, unfortunately it remains a weak point in the overall concept PX engine.

It is an ideal addition to all sport and racing cylinders. The intake control angle is relatively long with this crankshaft, which makes it more difficult to tune with SI24/SI26 carburetors than with a Stoffi or BGM crankshaft.
The long intake control time after top dead center ensures that in the lowest speed range much of the mixture already sucked in is pushed back through the carburetor (so-called This causes the mixture to become heavily greased and the engine runs unevenly and stutters. The ideal companion for this wave is therefore a larger carburettor which is inevitably accompanied by a longer intake stroke with this type of engine. This dampens the spitting back into the carburetor already relatively strongly, an additional mounted resonance chamber (so-called Boost Bottle) facilitates the adjustment of the engine additionally.
The larger carburetor cross section fits well to the long control angles of the shaft and makes a strong performance increase possible in the upper speed range opposite early closing crankshafts. Unfortunately also with losses in the engine elasticity.
The Mazuchelli shaft does not erect the same width at the rotary vane control cheek and at the shaft seal seat as the BGM shafts. Therefore the control slot in the engine housing cannot be extended as much as with a BGM crankshaft.

The additional stroke must be compensated for on cylinders designed for the series stroke of 57mm. For this purpose use either a 1.5mm head OR a 1.5mm foot gasket. It is not necessary to work with a 3mm gasket. The additional stroke of 3mm is distributed over 1.5mm in the direction of the bottom dead center and 1.5mm in the direction of the top dead center.

A foot gasket increases the control angle of the cylinder and thus creates the conditions for a sporty and speed-oriented performance. For full power, however, the exhaust angle must often be increased to compensate for the disproportionately increased overcurrent angle compared to the exhaust angle. For everyday engines it is usually recommended to compensate the stroke with a 1.5mm head gasket.

cylinders designed for 60mm stroke (Polini 221, Pinasco 225) do not require an additional compensating gasket.

Stroke: 60mm

Connecting rod length: 105mm

Motors: PX80, PX125, PX150, Cosa125, Sprint Veloce 150

Lift pin: 20mm (solid material)

Necessary stroke compensation: 1,5mm (foot or head on cylinders for 57mm stroke)

Conclusion: High quality material with long intake control angle for a very good turning ability as well as power increase in the upper speed range.

(US)
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€219.00 *

incl. VAT plus shipping costs

Available immediately (delivery time 1-3 working days*)

P For this item you get fidelity point/s

Bearings
sizes:	15x19x20mm
Gudgeon pins
diameter:	15 mm
Crankshafts
stroke:	60 mm
thread rotor side:	M12x1,25 right-hand thread
thread drive side:	M12x1,5 right-hand thread
diameter crankwebs:	98 mm
diameter bearing seat rotor side:	25 mm
diameter bearing seat drive side:	25 mm
diameter oil seal seat rotor side:	24 mm
diameter oil seal seat drive side:	31 mm
full circle crankshaft:
rotary valve crankshaft:
crankcase has to be milled:
engine casing has to be modified:
Connecting rods
length connecting rod:	105 mm
diameter small end connecting rod eye:	19 mm

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