Contained within the primary drive of the input shaft assembly of your VESPA motor are 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. If you want to install this kit yourself we have extensive instructions available for download on the righthand side.
We have repair kits available for every model of VESPA, from the V1 through to the PX'11.
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!
SIP-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!
SIP-Community user “tcpip” on art. no. 16020000: “Absolutely! If you're going to do a job, then you'd better do it right. If you've split your crankcase open, do it!”