Short fourth gear for Vespa PX and PX Lusso

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Better gear connection with a short 4th gear

Short fourth gear Vespa PX

Why install a short 4th gear in the Vespa?

The short fourth gear is installed to improve the gear connection to fourth gear and that works very well with the short 4th gear with 36 teeth!
The short 4th gear for Vespa PX engines makes sense for every requirement, whether for everyday drivers, tourers or racers.
With 36 teeth this is a gear one tooth shorter than the original fourth gear wheel of a Vespa PX200.

bgm PRO - Premium tuning parts

The bgm Pro gear parts are made of ultra-solid material. The gear wheels are made for the highest demands high-alloy NiCrMo case-hardened steel (20NiCrMo2-2 / AISI8620).
The very good base material withstands even the highest engine performance. The precisely defined surface hardening to 58-60HRC makes the pinions extremely resistant to wear. Always consistently high quality. No compromise.

bgm PRO short 4th gear

Advantages of a short fourth gear:

  • more relaxed driving,
  • smaller gear step,
  • higher gear ratio with further optimization of the transmission

4th gear -BGM PRO- Vespa PX Lusso T5 125cc, PX200 Lusso (short) - 36 teeth

Short 4th gear Vespa PX Lusso Suitable for all transmissions that have a flat gearshift cross. These gears can be seen on the main shaft, which have a circlip in front of the gear wheels.

 

4th gear -BGM PRO- Vespa PX old, PX200 (short) - 36 teeth

Short 4th gear Vespa PX old. Suitable for all transmissions that have a cranked gearshift cross. These gears can be recognized on the main shaft, which have a circlip in front of and behind the gear wheels.

 

The middle segment on which the switch cross rests is at

  • PX old (until 1984, cranked switch cross): 5mm
  • Lusso (from 1984, flat switch cross): 6,5mm

The middle segments of the BGM gear wheels are larger (approx. 1/10 mm) and thus offer even more contact surface for the gearshift cross.

Scooter Center Technology TIP:

The short fourth gear can be ideally combined with the stocky longer 64 teeth BGM Pro primary gear. The overall ratio is in connection with a 24T clutch pinion significantly longerthe Gear jump three to four but shorter. This means that the full engine power can also be used in Top speed be implemented.

bgm PRO short 4th gear

Advantages of a short 4th gear:

  • more relaxed driving,
  • smaller gear step,
  • higher gear ratio with further optimization of the transmission

When working on the gearbox, do not forget:

Especially interesting

So far, Malossi Sport and Polini 221 engines have emphasized combining with torque 24/64 reduction and a short fourth gear proven.

BGM6536L

By the short fourth gear, will the Gear jump from gear 3 to gear 4 reduced by a healthy amount, so that always with sufficient torque good aisle connection 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 speedy 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!)

Do not forget:

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