Primary gear ratio BGM PRO Vespa Largeframe

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Longer primary ratio for ever more power in Vespa engines

New performance and torque-focused engine concepts in the Vespa Largeframe Make the use of a segment longer primary translation almost inevitable.

A longer reduction stretches the available torque of your engine and the existing one Torque curve is more effective usable. This means that you can drive at the same speed at a lower speed or, conversely, you can do one higher top speed .

bgm PRO primary gears

Advantages of a bgm PRO longer primary for your tuned engine

  • more relaxed drivable
  • quieter transmission
  • lower fuel consumption
  • increases the top speed
  • With the short fourth gear, it even improves acceleration at higher speeds
  • greater durability due to the large overlap of the tooth flanks
  • lower speeds

Bisher the primary ratios available on the market were only available in a straight-toothed version. The resulting

  • clear running noise,
  • less overlap on the tooth flanks and
  • the fact that a subsequent change in the reduction can only be achieved again with increased effort,

reduce the benefit for everyday use.

NEW: Smoother running and more even power transmission with bgm PRO

The Primary gears BGM PRO are manufactured with helical teeth. The helical gearing offers in addition to one significantly smoother running a better and more even power transmission on the tooth flanks compared to a drive with straight teeth.

BGM6565 (2)

Tested quality from bgm PRO

The primary gears are based on per batch like our clutch pinions and gear wheels Dimensional accuracy, material quality and workmanship checked.

Wide range of possible combinations

We are currently the only manufacturer to offer reductions with helical gearing, which can be varied further with different clutch pinions.

The following variants are therefore possible:


Primary gear BGM BGM6564 Primary gear BGM BGM6565 *
Number of teeth 64 65
Clutch pinion BGM Cosa BGM6522S 22 2,91 2,95
Clutch pinion BGM Cosa BGM6523S 23 2,78 2,83
Clutch pinion BGM Cosa BGM6524S 24 2,67 2,71
* or original Piaggio


Vespa clutch pinion BGM PRO with 22 teeth

The Clutch pinion BGM PRO with 22 teeth However, it is a special form. The base circle and the tooth flanks of this pinion are optimized for use on a 65 and 64 primary gear. In the 22/65 variation, the BGM PRO offers coupling pinions a more stable and better coverage on the tooth flanks, as do, for example, Piaggio or Newfren pinions in this combination.

Fits immediately: bgm SUPERSTRONG clutch

Our BGM Superstrong Vespa clutch is already equipped with the appropriate pinions and can easily be installed on the BGM primary wheels.


Using the table, you can see how the reduction ratio changes with the various combinations. So you can give your engine the right gearbox for every occasion. Even with a 64-tooth primary gear that is suitable for long-distance journeys, thanks to the possible combination with a 22-tooth clutch pinion, an overall reduction can be produced that is shorter than that of an original PX200. You can then use different exhaust systems at any time. Either speed go! Or tractor style.

Vespa primary repair kit

For mounting the primary gears on the countershaft, we recommend our reinforced Primary repair kit BGM0195F44

The reinforced springs also permanently withstand significantly increased torque values.


Short fourth gear for Vespa

So far, the combination with 221/24 and one has been based on the torque-stressed Malossi Sport and Polini 64 engines short fourth gear proven.


By the short fourth gear, the gear jump from gear 3 to gear 4 is reduced by a healthy amount, so that with sufficient torque a good gear connection is always guaranteed and your scooter can pull through cleanly when shifting into fourth gear.

In the table below and the graph ** you can see how the difference works. With the longer reduction, you can already travel at a good speed for city or cross-country trips in the lower gears at a very low speed. In gear 4, the combination enables brisk travel at a reduced engine speed and the ability to reach a higher top speed.

24_64 graph



24_64 tab

** (At this point we would like to thank GSF member Motorhead for the Gear Calc!)


All in all, a longer primary makes your engine more durable

  • more relaxed drivable
  • increases the top speed and
  • With the short fourth gear, it even improves acceleration at higher speeds.



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