A racing crankshaft possesses, in contrast to its original cousin, a noticeably longer inlet port timing which increases the amount of combustible fuel charge delivered during each revolution of the motor. The webs on the crankshaft are modified and designed to improve the internal aerodynamics of the crankcase. This helps reduce turbulence and the gas-flow is accelerated and improved. The con-rods profile has also been optimised and usually possess a silver-caged bottom-end bearing to cope with the extra load and speeds. All crankshafts share a high-end small-end bearing as part of the delivery.
If you plan to include an electronic ignition in the set up of your motor we strongly recommend its combination with a racing crankshaft equipped with 20mm oil-seal and bearing seating diameters. This crankshaft has also proved its worth on motors fitted with performance cylinder kits due to the very stable crankshaft stubs. High revving motors, fitted with powerful race cylinders and/or lightened flywheels, are best equipped with the crankshaft originally found on the Vespa ETS models. The very thick crankshaft stubs prevent shearing caused by increased power output. To fit these crankshafts into the Vespa V 50/PV/ET-3/PK motor casings you will also require a conversion bearing and a suitably dimensioned oil seal kit.
Extra lubrication openings, with holes at the small-end and slots at the big-end, improve the oil supply to the con-rod bearings. This extends their effective life while simultaneously allowing higher revs to be safely and sustainably maintained.
Conclusion : A performance orientated crankshaft is not only useful in combination with a performance cylinder as standard set-ups can also benefit from the welcome boost in all-round power that these high-tech components provide!
Racing crankshaft / 51mm stroke / 97mm con-rod / 20/20mm / M12 thread
Racing crankshaft with an 82mm diameter flywheel-side web and an 87mm diameter disc-valve side web, 97 mm con-rod length, oil-seal seat diameter: 20mm, bearing seat diameter: 20mm, thick/blunt crankshaft stub profile with an M12 thread, includes con-rod bearing, machine-forged con-rod with lubrication holes around the small-end bearing position and slots for the big-end bearing, steel produced crankshaft webs, high-end con-rod washers, gas-flowed and profiled race crankshaft with performance optimised inlet port timings.
SIP -TIP : Do not forget to order fresh bearings, oil seals, woodruff keys and gaskets along with new holding nuts for both the flywheel and the clutch! Tools useful for this replacement job that we have available include : #27338000, #21070000 and #18119000. This crankshaft is also ideal if your motors set up includes a MALOSSI, POLINI, D.R. or PINASCO racing cylinder kit in combination with the Vespa disc valve inlet system.