Input Shaft Assembly 18-16-14-10 teeth BENELLI 4-speed/PK

Stefano BENELLI has been passionate about all possible petrol-driven vehicles, either two or four stroke, since the 1980's. His love of the two-stroke is strong and especially for the Vespa. This is where he could gather his first experience in motor tuning and many of his developments have seen successful use in scooter sprint racing. He found that the original Vespa gearbox was unable to cope with the extra power.

Back in the days when the only aftermarket gearbox component available here in Germany was a shorter 4th gear for the smallframe engine, the BENELLI range of gearbox parts were already being included in scooters racing in the Italian national racing series. In more recent times gearbox parts from a number of manufacturers have become available. Outside of his home country of Italy, parts produced by BENELLI were very hard to obtain and only a small exclusive circle of racers and tuners were even aware of their excellent reputation and existence.

During product comparisons conducted in Germany his gear cogs were rated better than those from other component manufacturers. Nowadays the BENELLI enterprise has become a small-scale producer of high-end gearbox components using the finest materials suited for a wide spectrum of potential employment. They have proven successful for use in off-road, circuit and sprint racing machines.

Certain problems from the largeframe models can also be experienced while riding the Vespa smallframes. The power-band of the motor cannot be used while accelerating from 3rd gear into 4th as the gear ratio gap is too large. BENELLI offer a number of useful solutions to this problem in smallframe engines with their new input shafts. Maximum revs in 4th gear while touring with a 150kg load, or the maximum power while accelerating in 4th while competing in sprint or circuit races. These shafts make everything possible.

The BENELLIinput shafts have proved their worth on numerous occasions and have displayed their lasting reliability. They also have an excellent performance/price ratio. There are different versions of this input shaft available, according to how close the gear ratios need to be for the requirements of the engine being tuned.

Conclusion: Smallframe Vespas used for sprint or circuit racing should not be without this quality shaft! An improved acceleration through the whole gearbox is also extremely useful while attempting the longer tours...

SIP-TIP: First set up the primary drive ratio to suit the whole transmission. This provides the basis on which you can then experiment with the choice of input shaft and sort out individual gear cogs and ratios. A new gear-selector spider (preferably also from BENELLI) and new gearbox oil should not be forgotten! Our SIP gear cog spacers help eliminate play between the cogs.

Input shaft with 20-17-14-10 toothed cogs: Can be ridden with the original set of gear cogs. The gear ratios between 2nd and 3rd and from there into 4th are closer along with a usable power-band in each gear while accelerating.

Input shaft with 21-18-14-10 toothed cogs: Can be ridden with the original set of gear cogs (58-54-50-46). A smaller gap between 3rd and 4th is the result and the difference between gear ratios smaller, improving acceleration.

Input shaft with 19-17-14-10 toothed cogs: Can be combined with only the first three of the original gear cogs (58-54-50). For the 4th gear a cog with 49 teeth will be necessary, which is already included with this input shaft kit.