SIP High-End Crankshafts by PRIMATIST for Lambretta engines with DL/GP Ignition—high-quality crankshafts for reliable engine operation and high-performance setups.
Together with the cylinder, the crankshaft forms the heart of every engine. It is one of the components subjected to the greatest stress. Converting reciprocating motion into rotational motion places the highest demands on quality and workmanship.
The shaft should also be well balanced to reduce vibrations. Oscillating masses should be kept to a minimum to support the engine’s performance.
The lower connecting rod bearing rotates at engine speed, is lubricated by the two-stroke mixture, and must absorb the load caused by the Piston’s change in direction twice with every revolution.
The crankpin, which connects the two crankpin shoulders and the Conrod, must be press-fitted with precise dimensions. If the press fit is too loose, the shoulders can twist relative to each other.
To ensure that sufficient mixture reaches the lower connecting rod bearing for lubrication, the lower connecting rod eye should be equipped with lubrication slots.
- Exceptionally low vibration
- Highly reliable thanks to high-quality material selection and precise manufacturing
- Available in various stroke and connecting rod lengths
SIP’s new crankshaft line is manufactured in Italy and meets these requirements. Special attention was paid to the highest quality and sophisticated design features. Each crankshaft is balanced to match the stroke, connecting rod length, and roller model.
The shafts are available in two versions. The Premium models come with a high-quality Conrod in the standard version, i.e., with an untreated surface. The Conrod is equipped with cooling slots and bores for the bearings.
The Performance shafts feature an extremely high-quality, polished Conrod. Polishing refines the surface, giving it a more stable structure that makes the Conrod more durable. Additionally, the polished surface reduces turbulence. The polished con rods are further weight-optimized. Their lateral contour is shaped for improved airflow, and they have been redesigned in the area of the lower bearing to provide even better cooling for the con rod bearing.
Lambretta Crankshafts
Crankshafts for Lambretta scooters in the LI/TV/SX/DL/GP series differ primarily in two characteristics: connecting rod length and the Cone on the LiMa side.
The large cone, measuring 25 mm directly after the oil seal seat, was originally installed only in the DL/GP engine. The small cone on all other models tapers to 21 mm immediately after the oil seal seat. Especially for high-performance engines, it is essential to use a shaft with the thick DL/GP cone.
Almost all Lambretta models were delivered with a 107-mm Conrod as standard. Only the TV 175’s Crankshaft had a 116-mm Conrod. The 116-mm Conrod has the advantage of running with less vibration. Many aftermarket cylinders are now available with a piston featuring a lower compression height—30 mm instead of 39 mm. This allows crankshafts with 116-mm Conrods to be installed on all LI/TV/SX/GP/DL Models.
SIP Lambretta shafts are available with 107-mm and 116-mm conrods, as well as with different strokes. Additionally, a distinction is made between the standard conrod variants (Premium) and the polished conrod (Performance).
We also offer 110 mm and 120 mm Conrds as special options. Both provide additional flexibility in selecting valve timing. The 120-mm Conrod ensures exceptionally smooth, low-vibration engine operation.
Conclusion: Very high-quality crankshafts for all applications, from high-end restoration to chasing lap times on the racetrack.
SIP TIP:
- When replacing the crankshaft, always replace the bearings and Oil Seals as well.
