Contained within the primary drive of the input shaft assembly of your VESPA motor

are six pairs of springs. These spring units are arranged so that the smaller springs

operate inside the larger springs for a stronger resistance to the forces created within

the drive train. If these springs are worn or even broken, acceleration will be interrupted

and effected with a jerky action similar to clutch failure. The only remedy is rapid replacement. 

Primary drive repair kits include outer and inner shock absorbing springs, outer and inner

cover plates and a set of rivets to hold it all together with the primary drive and the smaller

clog cluster of the input shaft assembly.

Conclusion: The primary drive assembly should be inspected and/ or replaced during any

major motor overhaul. Negligence will cost, in time, lots of money and riding fun!

TECH-TIP: Always install and replace ALL of the smaller primary drive components

during each major service. The securing plates on both sides of the primary drive,

input shaft holding nut, tab washer and also the input shaft needle bearings should

all be replaced for save and enduring use of your motor. Last but not least do not

forget to order fresh gearbox oil, gaskets and all relevant oil seals!