High-end Crankshaft for Vespa Largeframe Models. More stroke and top quality for high-torque everyday engines.
The Crankshaft, together with the Cylinder, forms the heart of every Engine. It is one of the most heavily stressed parts. The conversion from stroke to rotary motion places the highest demands on quality and workmanship. The Shaft should also be well balanced to reduce vibrations. The oscillating masses should be low to support the performance of the Engine. The lower connecting rod bearing rotates at engine speed, is lubricated by the two-stroke mixture and must absorb the load of the Piston's change of direction twice with each revolution. The Crankpin, which connects the two crank webs and the Conrod, must be compressed to exactly the right degree. If the pressure is too low, the crank webs will twist in relation to each other. To ensure that sufficient mixture reaches the lower connecting rod bearing for lubrication, the lower connecting rod eye should be provided with lubrication slots.
- Particularly smooth running
- Very high-quality materials and workmanship
- Available with polished forged connecting rod
The SIP Crankshafts
The Crankshaft line from SIP is manufactured in Italy and meets the highest demands placed on crankshafts. Particular attention has been paid to quality and sophisticated design features. The balancing of each Crankshaft is adapted to the stroke, connecting rod length and scooter model.
Crankshafts with a particularly long Conrod, designed for heavier 72 mm Pistons or which require more Counterweight due to a particularly long stroke, are additionally equipped with tungsten weights.
The shafts are available in two versions:
- The "Premium" Models are supplied with a high-quality Conrod in standard design, i.e. with an untreated surface, . The Conrod is equipped with cooling slots and holes for the bearings.
- The "Performance" Shafts are fitted with an extremely high-quality polished Conrod. Polishing refines the surface. This means that it becomes denser and has a more stable structure, which makes the Conrod more resistant. The polished surface also ensures less turbulence. The polished Conrods are further weight-optimized. Their lateral contour is more aerodynamically shaped and they have been redesigned in the area of the lower bearing for even better cooling of the connecting rod bearing.
The long-stroke Crankshaft PX 60mm
At 60 mm, the long-stroke Crankshaft for the Largeframe Vespa Models has 3 mm more stroke than the original crankshaft. This increases the displacement by approx. 5 %. The improved stroke/bore ratio not only increases performance, but also torque in particular.
This Shaft is designed to be particularly well suited to high-torque and everyday tuned Engines. The stroke of 60mm can be accommodated in the original crankcase, the SIP 60mm Crankshafts fit without adjustments.
The timing Disc Valve
The rotary valve crankshafts are available with two variants of intake timing:
- 115°/4°: quite close to the original timing. Particularly suitable for mild "road" tuning.
- 125°/-5°: with approx. 20° longer intake timing. The longer timing is very suitable for "sport" tuning.
- At the same time, the times remain within a frame that is still very suitable for everyday use. Engine performance is not lost in the lower rev range and can be easily tuned. The "sprayback" from the crankcase remains at a low level. The contour of the control cheek is designed to allow the gas to flow in as smoothly as possible.
In addition, this type of cheek design allows particularly effective balancing of the Crankshaft and therefore particularly smooth engine running.
The connecting rod lengths
We supply the Long Stroke Crankshafts with the following connecting rod lengths:
- 105 mm: for the 125-150 cc largeframe models
- 110 mm: for the 200cc class
- 127 mm: for the QUATTRINI M244/M232.
- The additional millimeter to the original Conrod length of the Quattrini Conrod makes it possible to vary the timing. Two small tungsten weights have been fitted here for perfect balancing with the Quattrini Piston.
Note: The SIP Crankshaft's rotary vane cheek has a particularly precise fit for smooth engine running. In conjunction with aftermarket casings or faulty rotary slide surfaces in the casing, contact between the Crankshaft and the casing may occur. Please check the dimensional accuracy before installation.
Conclusion: The ideal Crankshaft for mild, reliable tuning from the improved original engine to the Malossi Sport with box exhaust and 20 hp suitable for touring.
The best setup - our SIP-TIP:
- When replacing the Crankshaft, always replace the Bearing and Oil Seal as well. E.g. item no. M6615466 and M6617236.
- Compensate for the extra stroke with a 1.5 mm head gasket or use a Cylinder for 60 mm stroke.E.g. item no. 15060000.
- New reinforced Woodruff Keys are always a useful addition: Art. no. 87059200
