Racing crankshafts for Vespa 98/125/150/GS/160 GS/180SS
Racing Crankshafts are a simple and effective update for any Vespa engine. Racing Crankshafts are generally understood to be all crankshafts that deviate from the pure standard specifications. A racing shaft usually enables higher engine speeds. The Engine becomes more lively and agile. This results in better acceleration and a higher top speed. The long-stroke variants increase torque and power on the mountain. A racing crankshaft also makes the Engine more stable, smoother running or allows the use of a better Ignition. So why not treat an old lady to something good?
As already mentioned, we generally understand racing Crankshafts for Wideframes, GS160/SS180 and Motovespa Models to be all crankshafts that deviate from the pure standard specifications. These are
different crank web shape
more stroke
longer or reinforced Conrod
Clutch/pole wheel stub not intended for the original parts
optimised intake geometry due to shape and cut-out
Racing Crankshafts make higher engine speeds possible due to their cheek shape. Engine can deliver more power and improves acceleration and top speed. Turbulence and stalling are reduced. The Conrod is partly 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.
We generally refer to Racing Crankshafts with a longer stroke asLong Stroke Crankshafts. More stroke = more cc = more torque. The extra stroke is compensated for by thick gaskets, also known as spacers, on the Cylinder Head and/or cylinder base. This allows you to play with the timing.
If "only" the Conrod and Cone are changed, but the design itself corresponds to the original, we stick with the term Crankshaft.
The next decision criterion is the choice of the correct engine type.
Racing crankshafts for the first Vespa Models
The Engines of the first Vespa Models all have a direct inlet into the Cylinder. Therefore, the Crankshafts do not require a cut-out for controlling the Disc Valve.
A distinction can be made between the following engine groups:
125 cc, 50 mm stroke, 110 mm Conrod: These delicate Crankshafts breathe life into the first Vespa Models Vespa 125 V30-33T/U/Hoffmann HA/HB.
125 cc, 54 mm stroke, 110 mm Conrod: More stroke for the next generation of Vespa 125 VM1-2T/VN1-2T /ACMA 125 ACMA Paris, '51-'55 Vespas. The mushroom shaft becomes a full cheek.
150 cc, 57 mm stroke, 110 mm Conrod: The stroke for Vespa 150 VB1T/VGL1T/VL1-3T increases again with the number of cubic metres. These shafts can also be ridden on the VM/VN in conjunction with a 150 ccm Cylinder.
150 cc, 57 mm stroke, 105 mm Conrod: The top-of-the-range wideframes have a shorter Conrod and also a Cone on the clutch stub. They fit in all Vespa 150 GS and also in MOTOVESPA 150 S/Sprint/GS.
160-180 cc, 60 mm, 110 mm Conrod: The sports models of the 60cc Vespa 160 GS/180SS are long-stroke. Initially with bronze bushes, then with Gudgeon Pin Bearing.
Important: No PX Shafts fit into these Crankcases. However, if you ride a PX Engine in the Models, you must also look under PX/T5/Cosa.
More stroke - More torque - More fun
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 strokeif you want more torque, you can opt for long-stroke variants. For Racing Crankshafts, we refer to Crankshafts with a longer stroke as Long Stroke Crankshafts to make them easier to distinguish. There is a small selection of Long Stroke Crankshafts with 60mm stroke for the Vespa Wideframe. For the GS160/SS180 Models, 60 mm is the standard stroke.
Note: Stronger cylinder base or cylinder head gasket required. Additional stroke should only ever be compensated for using a head gasket with half the thickness of the additional stroke. If a base gasket is used as compensation, the exhaust must also be machined. However, this only makes sense for 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 also reduces the maximum piston speed and therefore also the change in speed of the Piston during one revolution. The timing also changes with a long connecting rod. However, only slightly, because 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 popular Conrods
105 mm: The standard Conrod of the GS 150.
110 mm: Was used as standard on Lampe Unten Models and on GS 160/SS 180.
115 mmis used on a few high-end Crankshafts. The additional length must be compensated for with a foot seal.
The Conrod is one of the most heavily loaded parts in an Engine. It has to transmit the force of the explosion, withstand extreme acceleration and endure great heat. In addition, two bearings run in the running surfaces of the Conrod, one at engine speed, so a high-quality Conrod is suitable and important to prepare an Engine for Elevation loads or to increase its stability. But how can you recognise a good Conrod and what are the structural differences that make it higher quality and more resilient?
The best-known features of high-quality Conrods:
Forged Conrods: Compared to standard Conrods, they have a better strength-to-weight ratio. They are therefore more stable for the same weight or lighter for the same stability.
Silver bearings: The quality of the bearings used is of great importance for the service life of the Crankshaft. Bearing with a silver-plated cage are often used for connecting rod bearings. This is intended to improve emergency running properties and wear behaviour through better heat dissipation and adhesion of the oil film.
Additional lubrication holes/grooves: Additional holes or grooves allow more Oil to reach the bearings. This not only provides additional lubrication, it also helps with heat dissipation.
Polished connecting rod/blade connecting rod: A polished Conrod not only looks good, the smooth surface should also reduce turbulence. A surface treated in this way is also denser and more stable.
Blade connecting rod: A blade connecting rod is designed to minimise turbulence and the air resistance of the Conrod.
there are a large number of features and combinations of the implementation of the properties on a Conrod. To make the selection a little clearer, we distinguish between three types of Conrod:
Standard: A good Conrod that has been manufactured to standard specifications.
Sport: An improved Conrod that has at least two of the features listed above.
Race: An elaborately manufactured Conrod that has at least four of the features listed above.
This simplified division into three categories is intended to help you orientate yourself in the large selection of Crankshafts and Conrods.
The better the Crankshaft, the more effective the balancing and the smoother the Engine will run
Strong vibrations not only have a negative effect on riding comfort, they also affect the durability of the individual components on a scooter and, last but not least, the performance of an engine. This can be remedied by "finely balanced" Crankshafts. "Finely balanced" is not actually a clear technical term. It is more of a colloquial term for a particularly well-balanced Crankshaft. Nevertheless, we have decided to use this term to provide information about a Crankshaft. We use the term "finely balanced" to describe Crankshafts that fulfil all three points mentioned above:
They are particularly precisely aligned.
They oscillate at 12 or 1 Clock.
The manufacturer has realised a certain balance factor in the design.
Unfortunately, this is no guarantee that the balancing of the respective Shaft will be optimally matched to the intended Engine. But it is a clear sign of quality, which greatly Elevates the likelihood of a smooth-running Engine.
Our top brands for Crankshafts for Vespa 98/125/150/GS/160 GS/180 SS
SIP PERFORMANCE:high-end Crankshafts designed by the top tuners of the German-speaking scene and manufactured in Italy in a noble crankshaft forge. As SIP Performance version with polished forged Conrod or in the Premium version with a high-quality bronze Conrod.
DRTfor a long time the only supplier for wideframes. Good quality "Made in Italy", also offers special solutions for wideframe models.
Customers ask - SIP answers
"Do I compensate for the extra stroke of a Long Stroke Crankshaft with a head or foot seal?"
In principle, the extra stroke should be compensated for with a head gasket (0.5 x difference to the original stroke (e.g.: 60 mm-57 mm = 3 mm x 0.5 = 1.5 mm gasket)). With the head gasket, the timing increases only slightly and the characteristics of the Cylinder are retained. If a base gasket is used, the timing increases relatively sharply. However, the advance flow decreases at the same time. This results in an unfavourable ratio. This only makes sense if the exhaust is additionally machined.
Technology tips
If you want to delve even deeper into Crankshaft technology, we recommend our Technology blogs.