Crankshafts for Lambretta - Racing crankshafts
Racing Crankshafts are an effective update for every Lambretta Engine. By Racing Crankshaft we generally mean all crankshafts that deviate from the pure standard specifications. The basic requirements for perfect engine tuning are minimum manufacturing tolerances, high speed stability, low bearing play and durability of the crankshaft. A Racing Crankshaft 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 hills. A racing crankshaft also makes the Engine more stable, smoother running or enables the use of a better Ignition. So why not treat an old Lammy to something good?
As already mentioned, racing Crankshafts for Lambrettas generally refer to all crankshafts that deviate from the standard specifications. These are
different crank web shape
more stroke
longer or polished Conrod
Clutch/pole wheel stubs are not intended for the original parts
optimised intake geometry due to shape and cut-out
Racing crankshafts are also characterised by particularly resilient materials, high-quality bearings, special Conrods, special balancing or weight.
We differentiate betweenRacing Crankshafts and Long Stroke Crankshafts. As Lambretta Engines have a direct inlet into the Cylinder, the shape of the Crankshaft is not influenced by the requirements of an inlet into the crankcase.
We refer to Lambretta Racing Crankshafts with a larger stroke asLong Stroke Crankshafts. More stroke = more displacement = more torque. Long Stroke Crankshafts are available in a wide range of variations. 60 mm stroke is by far the most popular, as 60 mm shafts can normally be installed without any changes to the Casing. Long Stroke Crankshafts with more than 60 mm stroke require a crankcase with an enlarged diameter.
The next decision criterion is the choice of the right engine type.
The right racing crankshaft for the respective Lambretta class
Due to the strong power delivery of tuned Lammys, only racing crankshafts with a thick fan wheel cone make sense here.
125-200 cc, 58 mm stroke, 107 mm Conrod: The Crankshafts for the top-of-the-range Lambretta DL/GP 125-200 cc models with the large 25 mm Cone.
These Crankshafts are ideal for tuning purposes. Today, almost all Engines are fitted with this Cone. They are also suitable for reliable everyday use and, when used with a DL/GP Ignition, also fit the Lambretta Series 1-3 Engines and therefore all Lambretta 125 LI/LIS/150 LI/LIS/SX/175 TV 2°-3°/200 TV/SX Models.
More stroke = more cc = more power
If you want more torque, you can opt for long-stroke versions. We refer to Racing Crankshafts with a longer stroke as Long Stroke Crankshafts to make them easier to distinguish.
-60 mm: Very popular for adding more stroke to an Engine. These shafts usually fit into the original Crankcase without modification. If a high-quality Shaft is used, it is an upgrade without side effects.
-62 mm: From 62 mm stroke, the Crankcase must be adapted to the larger diameter of the Crankshaft.
Note: Stronger cylinder base gasket or cylinder head gasket. More stroke should be equalised using a head gasket with a thickness equal to half the additional stroke. If a base gasket is used for equalisation, the exhaust should also be machined. 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. However, this advantage comes at the price of a drastically higher crankcase volume. A longer Conrod reduces the maximum piston speed, thus also reducing the speed change of the Piston during one revolution and ultimately the vibrations.
With a long Conrod, the timing changes only slightly. The Conrod length is usually measured from centre eye to centre eye.
A distinction is made between standard connecting rods , e.g. a forged connecting rod, or a polished cutter connecting rod, which are flow-optimised.
In older Lambretta Models, brass bushings were installed as Gudgeon Pin Bearing to minimise friction. Due to the high proportion of oil in the mixture and very low engine speeds, it used to be possible to ride quite reliably. However, as modern Engines reach higher engine speeds and less Oil is added, Needle Bearings are now generally used at the top and bottom of the Conrod. These can withstand higher speeds. In Racing Crankshaft engines, they are supplied with mixture through additional lubrication holes or slots. This reliably prevents a Bearing from running "dry", becoming too hot and seizing on the Piston or connecting rod pin. In high-quality silver bearings, the cage is silver-plated to ensure less friction, wear and a longer service life.
The most common connecting rod lengths are:
107 mmthe standard length of almost all models, with the exception of the TV 175. It is possible to install a Crankshaft with a 110 mm connecting rod instead of the 107 mm connecting rod. This should result in smoother engine running. The longer Conrod should then be compensated for with a 3 mm foot gasket. However, the difference between 107 and 110 mm is very small.
110 mma popular length for tuning shafts. It makes it easier to adjust the timing and is said to be somewhat smoother than 107 mm. It is better to convert to a Crankshaft with a 116 mm Conrod.
116 mmvery useful for tuned Engines. The additional length can easily be compensated for by a Piston with 30 mm compression height.
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 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 listed below:
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 is optimised for 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 Lambretta
SIP PERFORMANCEyou can't treat your Engine to anything better. The outstanding quality is unique in the Lambretta market.
MAZZUCCHELLI: Good and affordable Racing Crankshafts. Particularly popular in the Lambretta sector as an original replacement. Made in Italy.
Technology tips
If you want to delve even deeper into Crankshaft technology, we recommend our Technology blogs.
Customers ask - SIP answers
"Which connecting rod length is recommended?"
Most Lambretta shafts have a connecting rod length of 107 mm. This is quite short for a stroke of 58 mm or more and can cause vibrations. 110 mm Conrods hardly bring any improvement, but are easy to install and improve the possibilities for varying the timing. The best solution for most Lambretta Engines is a 116 mm Conrod. For almost all Cylinders on the market we have Pistons with 30 mm instead of 39 mm compression height. This allows a 116 mm Conrod to be perfectly balanced.
