Crankshafts for Vespa 125/150/Rally from '57 onwards
There is a wide range and variety of Crankshafts for the Largeframe Vespas of the 60s and 70s. If you want to keep your Engine original, use the standard Crankshaft. The first largeframes can be converted to Crankshafts with PX stump and are therefore more robust and ready for an electronic Ignition (depending on the type also for the use of a PX Clutch). However, the weak Vespa engine is longing for more Silencer. The Racing Crankshaft Disc Valve manages without changing the intake on the Crankcase. Fans of Reed Valve control and thus significantly more power will find what they are looking for in the Racing Crankshaft diaphragm.
Which Crankshaft should it be? Standard or race?
The different crankshaft types for the Vespa 125/150/Rally '57 Models:
Standard crankshaft
Standard crankshafts are replicas of the originals. To compensate for supply bottlenecks on the part of the manufacturer, we have several companies in our programme. The Oldie shaft with PX fan gear stub allows the use of an E-ignition in the original Crankcase. In old engines, the Crankshafts are often fixed or the Disc Valve is rusted. Bearing and shaft seal seats are often worn, the connecting rod bearings are worn or the cones and keyways are defective. In such cases, the Crankshaft should also be replaced during an engine overhaul.
Racing crankshaft: Disc Valve
Racing Crankshaftsusually have extended timing, polished crank webs and, in some cases, polished Conrods. Racing Crankshafts are a simple and effective tuning step for any rotary valve engine. A Racing Crankshaft enables higher engine speeds. The Engine becomes livelier and more agile. This results in better acceleration and a higher top speed. In contrast to the original Crankshaft, a Racing Crankshaft almost always has a significantly longer intake time. The crank webs are aerodynamically optimised and often polished. Turbulence and stalling are reduced. The Conrod is sometimes a forged connecting rod with additional lubrication holes or a polished knife-edge connecting rod. The lower connecting rod bearing is a silver bearing. All Crankshafts are supplied with upper connecting rod bearings.
Largeframe Racing Crankshafts with a larger stroke are referred to as Long Stroke Crankshafts. More stroke = more displacement = more torque. The extra stroke is compensated for by Spacers (thick gaskets) on the Cylinder Head and/or Gasket Cylinder Base. This gives you the option of simply playing with the timing.
Flowed Racing Crankshafts or Long Stroke Flowed Crankshaftsare Crankshafts whose intake-side crank web is machined to optimise flow. In most large-frame Engines, the intake sits above the crank web on the clutch side. A particularly flow-optimised machining of this crank web often resembles the shape of a lip.
Racing crankshaft: Reed Valve
Crankshafts whose design does not allow the use of the original rotary valve inlet are referred to as diaphragm crankshafts. A different type of intake control, usually a diaphragm, must be used. Diaphragm shafts are also available in different designs.
Full Circle Crankshaftshave, as the name suggests, two completely closed cheeks. A large diaphragm inlet is required here. It only makes sense to use a Full Circle Crankshaft in conjunction with a direct inlet into the Cylinder. These shafts are also available with a long stroke. The basic idea behind the Full Circle Crankshaft is better pre-compression, which is achieved via the completely closed crank webs. However, in engines controlled via the Casing, even large milled diaphragm inlets with boost ports cannot prevent the mixture from being unfavourably obstructed by the cheek standing in the way.
Flowed Crankshaftsare flow-optimised reed shafts that harmonise very well with reed intake manifolds. In most large-frame Engines, the intake sits above the crank web on the clutch side. A particularly flow-optimised machining of this crank web often resembles the shape of a lip.
TheBell-Shaped Crankshaftor mushroom crankshaft, is a crankshaft whose shape resembles a bell or mushroom. It also offers the mixture as little resistance as possible. Not quite as uncompromising as the Flowed Crankshaft, but the shape is symmetrical and the crankshaft is easier to balance.
Special racing crankshafts
Special crankshafts are manufactured for special Crankcases and do not fit into the original Casing. The SIP-BFA Crankcases are outstanding here. The massive Crankshafts are the key to the brute power of the 306 cc tuning.
The next decision criterion is the choice of the right engine type.
Few engine types for Vespa 125/150/Rally '57, but a wide range
A distinction can be made between the following engine groups:
125/150 cc, 57 mm stroke, 105 mm Conrod: The first Vespa largeframes Vespa 125 VNB/GT/GTR 1°/Super/TS/150 VBA/VBB/T4/GL/Sprint/V 1°/Super 1° still come with a narrow Cone on the fan wheel side. It is only suitable for tuning to a limited extent, as the Cone is weak. If you want to use these Vespas an electronic Ignition you need one with a matching Flywheel or use a "conversion Crankshaft" that uses the PX stub on the ignition side (e.g. art. no. 45135000).
The thicker fan sprocket stub of the later PX comes with the following models Vespa 125 GTR 2°/TS 2°/150 Sprint V 2°/Super 2°. All Crankshafts of the PX125/150 fit here. The range is large.
180 cc, 57 mm stroke, 110 mm Conrod: The Vespa 180-200 Rally with the first electronic Femsatronic Ignition gets a new Crankshaft. SIP produces a small series for these beautiful models with a Premium standard shaft.
200 cc, 57 mm stroke, 110 mm Conrod: the queen among the sports models of the 70s. The Vespa 200 Rally VSE1T 33997 ->. The Crankshaft of the later PX200 is used here for the first time. The tuning possibilities are enormous and popular. The range is therefore also very large and varied.
Note: Installing a PX Engine in the older models is also popular. With a 200cc Engine in particular, every vintage scooter becomes a powerful and reliable touring bomber or racer. Then it is best to set the scooter type Filter on the PX/T5/Cosa models.
More stroke = more cc = more power
Standard stroke: In addition to the cylinder diameters, the original engine types differ in terms of stroke, as we have listed in the engine classes.
Long stroke: If you want more torque, you can opt for long-stroke variants. In the case of Racing Crankshafts, we refer to crankshafts with a longer stroke as Long Stroke Crankshafts to make them easier to distinguish. When looking for long-stroke variants of the diaphragm shafts, you need to pay attention to the stroke lengths. Crankshafts with a 60 mm stroke are particularly popular.
There are also versions with even more stroke. With these Crankshafts, the diameter of the crankcase usually has to be adapted to the larger diameter of the crank webs.
Note: Stronger cylinder base gasket or cylinder head gasket required. More stroke is usually compensated for with a head gasket half the thickness of the additional stroke. Our favourite for 60 mm long stroke: 1.5 mm head gasket.
If a base gasket is used for compensation, the exhaust should also be machined. This makes sense, especially with higher tuning levels.
The subtle difference lies in the Conrod
A longer Conrod does not change the stroke, but the Cylinder must still be raised accordingly. The longer Conrod has the advantage that it is less inclined at half the stroke and the piston therefore exerts less lateral force on the cylinder wall, resulting in less friction. A longer Conrod reduces the maximum piston speed and therefore also the change in speed of the Piston during one revolution. This reduces the vibrations.
The timing also changes with a long connecting rod. However, only slightly, as the piston elevation curve changes slightly. As the crank webs are held together by the Crankshaft Pin, it is desirable to have the highest possible pressing dimension to prevent the two webs from twisting. The connecting rod length is always measured from centre eye to centre eye.
The most common connecting rod lengths are:
- 105 mm: The standard length of the original Conrods of 125-150 cc Models.
- 110 mm: The standard length of the 180-200 cc Rally Models.
- 126/127 mm: Large-volume cylinders can be installed on the Rally 200, which must be operated with such special connecting rods, e.g. Quattrini M244.
A distinction is also made between standard Conrods and polished cutter Conrods , which are flow-optimised. High-quality Conrods have additional lubrication holes or slots in the area of the bearings in order to better supply them with mixture. This provides reliable protection against a bearing running "dry", becoming too hot and seizing up on the Gudgeon Pin or connecting rod pin. In high-quality silver bearings, the bearing cage is silver-plated to minimise friction and wear and thus ensure a longer service life.
Our top brands for Crankshafts for Vespa 125/150/Rally models from '57 onwards
MAZZUCCHELLI: Good and favourable standard and Racing Crankshafts for Largeframe. Made in Italy, popular special models for converting oldies to electronic Ignition.
SIP SPARE PARTS: Special small series for Vespa Largeframe in top quality. The perfect update for original and slightly tuned engines in top quality: "Made in Italy".
SIP PERFORMANCE: Developed by the brightest minds at SIP and produced in a high-tech tuning forge. The best thing that can happen to a classic Engine. The highest quality on the market across all tuning levels, naturally "Made in Italy".
POLINIinteresting Shafts with partly complex balancing. Not available for 125 VNB/GT/GTR 1°/Super/TS/150 VBA/VBB/T4/GL/Sprint/V 1°/Super 1°.
PINASCO: Good shafts from Italy with interesting options for stroke and quality levels, but only for PX-compatible Engines.
Technology tips
If you want to delve even deeper into Crankshaft technology, we recommend our Technology blogs.
Customers ask - SIP answers
"What other parts do I need for a crankshaft replacement?"
Often only cent items, but annoying if you don't replace them:
Woodruff Keys - don't put an old Woodruff Key in a new groove
Gasket Set Engine - if you don't change it, it will drip
Crankshaft bearings - always replace LIMA as well as CULU side
Oil Seal Crankshaft - replace both sides here too
NutLock Cap - if you have a Castle Nut on the clutch, you need it
