The gear selector is one of the most hard working components in the Vespa smallframe motor. It is responsible for the transfer of power through the drive train between the gear cogs and shaft within the output shaft assembly. The more performance a motor can deliver, the more gear changing is necessary in order to exploit fully the available performance. This, in turn, means the gear selector requires replacement at shorter intervals than in a more moderately tuned motor. All gear selectors require replacement, irrelevant of state of tune after 10-12000 kms (6-7500 mls.). Wrongly dimensioned or defective gear selectors, incorrectly assembled gear cog clusters, loose input shafts or excessively large end float distances can all shorten drastically the effective working life of your gearbox and with it the rest of the motor. The gearbox slowly gets more and more 'jumpy' and with it your nerves. For these reasons and more it is recommendable to replace the gear selector during every service of your engine.
We recommend the use of original PIAGGIO gear selector in your gearbox. If you are looking to save a few pennies there are also slightly less expensive after market items available produced by RMS and FA ITALIA. The specially hardened item produced by DRT is most definitely recommendable for use in the more highly tuned motor projects.
The gear selector originally used in 3-speed gearboxes had only two engagement arms, the later models possess four. The difference between the gear selector in 4- speed motors that one of the versions is rounded, the other squared. The different positions at which the gears and/or the neutral position is achieved highlight the fundamentally opposing design features of the two gear selector that do the job in the 4-speed gearbox. If the incorrect version is used your engine will deliver its power like a pogo stick, thats if you can stay on long enough... The compatibility can be quickly checked by pre-assembling the output shaft gear cog cluster and testing whether arms of the gear selector engage the recesses provided for the neutral part of the gear assembly, which is luckily simply confirmable with the small frame motors gearbox set up. The complete assembly can be suspended vertically in the jaws of a vice and the gear selector mechanism can then select each gear cog individually to check that the arms of the gear selector engage correctly within the recesses on the internal diameter of the gear cogs.
Conclusion: If you want to save money anywhere, this is the wrong place. A new gear selector belongs in every toolkit!
SIP-TIP : The thing that really counts during the assembly of the small frame motors output shaft is to measure precisely and adjust correspondingly the end float after the cogs have been (correctly)arranged in place on the gear cluster. Do not forget to order fresh gearbox oil for successful completion of this conversion. The suitable output shaft assembly tool (Art. No. : 63791000) makes this job a whole lot easier and quicker.
SIP community user 'vespaandmore' on Art. No. : 11158900 "Best quality and fits great!"