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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
Now finally have an optimal gear connection from 3rd to 4th gear!

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 longer the 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
Now finally have an optimal gear connection from 3rd to 4th gear!

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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Vespa gear shims spacer shoulder ring

Shoulder rings gear shims bgm PRO for Vespa and Lambretta

Distance Vespa transmission & distance Lambretta transmission

Here we show you how to properly distance the Vespa gearbox: Discuss the Vespa gearbox

To compensate for excessive backlash in the gearbox, you need shims of the appropriate thickness. We have these for Vespa and Lambretta engines high quality shoulder rings from bgm PRO included in our program.

The hardened and ground Compensating washers for spacing the gearbox generally have a tolerance of only + 0 / -0.04mm and are subjected to an extensive test in production per batch.

 

SI Faster Flow 004

 

Vespa gear shims / spacers / shoulder rings

Vespa Rally, Sprint, VNB etc.

Lovers of the elderly Vespa Largeframe Models like Vespa Rally, Sprint & Co can be pleased: the matching shoulder rings are in the range for these gears 2mm to 2,50mm finally available again thanks to bgm PRO.

As with the more stable Vespa PX Lusso variant, the shoulder rings have 4 lugs for locking. The knocking off of the individual nose is therefore no longer possible in the new design.

BGM6020S20

The shoulder rings for the older 3 and 4-speed gearboxes (recognizable by the fact that only one shoulder ring is required on the shift pin side), we have made for you in the standard dimensions.

BGM6020

Vespa PX Lusso and Vespa Smallframe

For the Vespa PX Lusso and Vespa Smallframe Transmission In addition to the standard sizes from 1,00mm to 1,40mm, we also offer the shoulder rings with 0,9mm. This dimension is often required for retrofitting the main shafts with other gear wheels in order to restore the correct play or if you want to use the stronger circlips according to DIN.

BGM6020_1

The bgm PRO shoulder rings are hardened and ground in parallel so that your gear unit reliably maintains the set play for a long time.

 

Gear spacer Vespa bgm PRO

bgm PRO shoulder rings

  • hardened and ground in parallel
  • Tolerance of only + 0 / -0.04mm
  • many strengths available
  • for clean shifting
  • and a durable transmission

 

Here you get clean switching operations

 

Lambretta gear shims / spacers / shoulder rings

For the Lambretta gearbox, we can also offer you gear spacers in several strengths.

BGM6020_2

 

Gearbox shim -BGM PRO- Lambretta series 1-3

 

 

 

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Distancing the Vespa gearbox - very easy - instructions

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So you can easily disassociate your Vespa transmission

In order to adjust the play of the gear wheels on the main shaft, you need the corresponding Gear shims and for measuring the transmission, for example, this Feeler gauge in duplicate (2x) (!!)

vespa-gear-distance-feeler-gauge

It is best to start so that the gears will hold securely in the installed state and the transmission can be shifted cleanly into neutral in first gear with a shoulder ring of normal size 1,0mm.

BGM6020 004

If you start with too strong a shouldering under first gear, it could be that the gearshift cross is no longer free between the segments of the gear wheels and wants to thread into the gear wheels in neutral.

BGM6020 015

Therefore, it makes sense to first make the necessary compensation behind fourth gear to place.

BGM6020 002

Check gear play

You can now use the feeler gauges to check the play of the gear wheels.

The installation clearance should be in the range between 0,05mm and 0,15mm lie. In the case of gears that consist entirely of new parts, you can choose the game tighter, as all components are still getting used to each other.

BGM6020 006

Don't choose too little game

However, you shouldn't mean it too well and choose the game too narrow. In operation you achieve exactly the opposite. The hardened surfaces of the gear wheels and shoulder rings then tend to seize and so drastically increase the play within a short time.

If you are single Gear wheels If you want to swap from your gearbox, it is advisable to get one directly Set of shoulder rings in the range of 1,0mm to 1,3mm to be ordered.
And if you're at it anyway, you also have a look at that Switch cross on. Don't skimp on Gear oil and immediately use something new – and equate new seals .

Good tool, suitable for your scooter, always makes work easier.

BGM6020 019

Gear spacer Vespa bgm PRO

bgm PRO shoulder rings

  • hardened and ground in parallel
  • Tolerance of only + 0 / -0.04mm
  • many strengths available
  • for clean shifting
  • and a durable transmission
Here you get clean switching operations
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Vespa gearshift cross

Gearshift cross Vespa bgm PRO

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Vespa gearshift cross

The bgm PRO switch cross is the finest material for high demands.

Made from high quality 15CrMo5 (SCM415) chrome molybdenum steel.
This Vespa gearshift cross is very resistant, but offers elasticity to protect the gear flanks.

We are enthusiastic about the quality always guarantee consistently high Top quality.

Can be used for all types of stress, regardless of whether you are an everyday driver, Sunday driver, tourer or racer.

Gearshift cross -BGM PRO- "Vespa old"

Vespa gearshift cross PX Alt BGM6501A

Vespa PX old 80 ccm (V8X1T up to No. 100230), 125 ccm (VNX2T up to 232052), 150 ccm (VLX1T up to 624301), 200 ccm (VSX1T up to 315266), Rally180 (VSD1T) (from 26849), Rally200 (VSE1T) (from 4476), Sprint (from 1170240), Sprint Veloce (from 1693

Article no. BGM6501A

Buy Vespa PX Alt gearshift cross

Gearshift cross -BGM PRO- “Vespa Lusso”

Vespa gearshift cross PX Lussi BGM6501L

Vespa PX Lusso 80ccm (V8X1T from No. 100231), 125 ccm (VNX2T from No. 232053), 150 ccm (VLX1T from No. 624302), 200 ccm (VSX1T from No. 315267), T5 125cc, Cosa

Article no. BGM6501L

Buy Vespa PX Lusso gearshift cross
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