A points ignition system is prone to failure. When used in tuned motors and on longer tours they represent a risk to the overall reliability. For these reasons and more they are often replaced by an electronic ignition system. Fans of the Vespa 125 VNB/GT/GTR/Super/TS/150/VBA/VBB/VGLA/B/GL/Sprint/V/Super models have, up till now, had the dubious pleasure of being forced to use the Indian produced BAJAJ ignition system or the expensive, high-end solution provided by a VESPATRONIC system. After persistent requests for help by the people at STOFFI's garage we decide to see what we could do to assist.
The solution we came up with is an amalgamation of two existing crankshaft types. The basis is provided by the original Sprint crankshaft assembly, including the original oil seal and bearing collar diameters. This is then altered at the MAZUCHELLI factory to include a modified flywheel side crankshaft stub originating from the PX range crankshaft assembly. The existing clutch side of the crankshaft remains untouched and in place. Alongside this SIP crankshaft that enables an improved choice of ignition systems with oil seal and bearing collar diameters identical to the original items, we also have a race version available. Its extended inlet port timings provide the original Sprint motor with a welcome boost of extra power. The long-stroke version with 60mm stroke and identical timing as the standard makes everybody smile: a big increase of the torque change the originally weak scooter into a tractor.
Due to the manufacturing tolerances of the crankcases the stator plate could misalign with the flywheel during assembly and cause ignition problems, to alleviate this potential problem we recommend the use of suitable stator plate spacers.
Conclusion : A perfect solution for electronic ignition upgrade conversions and crankshaft tuning projects for the Vespa Sprint motors.
Racing/ Long stroke crankshaft/ 57/ 60mm stroke/ 20-25mm/ M 12
Crank shaft enabling the use of PX ignition systems, 95mm diameter flywheel side crank web, 97.9mm diameter clutch side crank web, oil seal collar diameter 20mm, bearing collar diameter 25mm, blunt shaft stump from the PX motor on the flywheel side with a M12 thread, small end bearing is included in the delivery.
SIP-TIP : Do not forget to order new woodruff keys, a M12 securing nut and its safety washer. To complete the conversion properly you should also order a PX Lusso stator assembly and a PX type flywheel to match such as a SIP Touring, PX 200 or the lightweight HP4 version. The stator plate spacer (Part No. : 50011300) could prove useful!
Robert Zinnöcker 'Zini'. STOFFI-SIP racing team:
'We've been waiting for this for years. At last the ignition systems on Vespa Sprints can be reliably and relatively cheaply upgraded to an electronic ignition system, perfect!'