SIP Performance crankshaft: DL/GP large taper, 58 x 107mm
A high-end crankshaft for Lambretta engines equipped with a DL/GP ignition.
In combination with the cylinder, the crankshaft represents the heart of every motor. It is one of the hardest working components and the conversion of the pistons stroke to rotary movement demands the highest quality and level of precision manufacture for enduring use.
A well-produced crankshaft should also be correctly balanced to reduce vibration in the motor and the oscillating masses should be kept low to facilitate an improved performance from the motor. The big end bearing rotates at the same rate as the motors rpm, receives lubrication from the two-stroke oil contained within the fuel mixture and has to convert the pistons abrupt change of direction twice during every single revolution of the motor.
The crank pin, that connects both the crank webs with the con rod, requires pressing together during assembly to a precise stiffness, to avoid the crank webs to become misaligned during operation. To enable the fuel mixture to adequately lubricate the big end bearing the lower eye of the con rod should be provided with lubrication slots.
Particularly low vibration
Very reliable due to the choice of materials and production
Available with different stroke and connecting rod lengths
This brand-new range of SIP crankshafts are 100% 'Made in Italy' and easily fulfil all of the above listed requirements, especially concerning the high-end quality and well-conceived constructional features. Every single crankshaft is balanced to be compatible with the stroke, con rod length and model of scooter to which it is fitted.
We have two versions of these crankshafts available. The 'Premium' models are equipped with a high end 'standard' type con rod, meaning that the surface is left untreated. This version of the con rod also possesses lubrication slots and holes for both the big and small-end bearings respectively. The 'Performance' crankshafts however have an extremely high quality con rod included. The polish it receives upgrades the surface finish, providing it with a more stable molecular structure which makes the con rod tougher and more enduring. The smoother surface finish also helps reduce the turbulence in the motor, while simultaneously saving a lot of weight. They have a gas-flowed profile and have a revised big-end design, improving the lubrication of the bearing located there.
The crankshafts we have produced for all Lambretta LI/TV/SX/DL/GP models can be distinguished by two main features: The total length of the con rod and the flywheel-side crankshaft stub diameter.
The sturdier original stub types with 25mm diameter (measured from the shaft oil seal seating) were only included with the DL/GP motor design, the smaller stub, that found use in every other models engine, narrows immediately to a paltry 21mm at the same point. This makes the fitting of the thicker DL/GP type crankshaft type obvious, if not essential, in all tuned Lambretta motors!
Almost all Lambretta models were produced including a con rod with a total length of 107mm in the motor. Only the crankshaft fitted to the Lambretta TV 175 possessed a con rod that was 116mm long, which brought with it the added advantage of a noticeably smoother running motor. In recent times many tuning cylinders have become available optionally including a piston with a reduced compression height (30mm instead of 39mm). This enables the fitting of a crankshaft with a 116mm con rod in all Lambretta LI/TV/SX/GP/DL motors.
The SIP Lambretta crankshafts are available with either a 107mm or 116mm con rod and various stroke lengths. Additionally the choice is also possible between a standard (Premium) or polished (Performance) type of con rod with the crankshaft assembly.
We offer 110mm and 120mm as special connecting rods. Both allow some leeway in the choice of timing. The 120mm connecting rod ensures a low-vibration engine run.
Conclusion: Very high quality crankshafts for universal operation, from high-end restoration projects all the way through to shaving lap times on the race track!
SIP - TIP: Do not forget to change the crankshafts bearings and oil seals when replacing or servicing the crankshaft!