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BGM PRO shoulder rings and gearbox shims for Vespa and Lambretta

Shimming Vespa & Lambretta transmissions

Here we show you how to properly shim the Vespa transmission: shimming Vespa transmissions

In order to balance out too much free play in the gear box you need shims in the corresponding thickness. We have introduced these high quality BGM PRO shoulder rings for Vespa and Lambretta engines to our programme.

The hardened and grounded transmission shims generally have a tolerance of just +0/-0.04mm and during manufacture each batch is subject to comprehensive testing.

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Vespa shims/ spacers / shoulder rings

Vespa Rally, Sprint, VNB etc.

There is reason for enthusiasts of the older Vespa Largeframe models like the Vespa Rally, Sprint & Co. to be pleased: for these gearboxes, the fitting shoulder rings ranging from 2mm to 2.50mm are finally available again, thanks to BGM PRO.

The shoulder rings feature, as is the case for the stronger Vespa PX EFL version, 4 nibs for locking in. Hence, with the new production design it is no longer possible to chop off an individual nib.

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We had the shoulder rings for the older 3 and 4 speed gearboxes (can be identified by the single shoulder ring that is required on the shifter bolt side) manufactured for you in standard dimensions.

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Vespa PX EFL and Vespa Smallframe

For the Vespa PX EFL and Vespa Smallframe gearboxes we offer the shoulder rings in standard dimensions from 1.00mm to 1.40mm and additionally also in 0.9mm. This dimension is often required when converting the sprockets on the main shaft in order to restore the proper free play but also in case you wish to use the stronger circlips according to DIN.

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The BGM PRO shoulder rings are hardened and ground parallely so that your transmission keeps the adjusted free play reliably and for a long period.

Vespa BGM PRO transmission shims
BGM PRO shoulder rings

  • hardened and grounded parallely
  • just +0/-0.04mm tolerance
  • available in many thicknesses
  • for a precise gear change
  • and a long lasting gearbox
You get precise shifting here

Lambretta shims/ spacers / shoulder rings

For Lambretta gearboxes we can offer you transmission shims in different thicknesses as well. BGM6020_2

Gear box shim -BGM PRO- Lambretta series 1-3

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Vespa transmission shimming – really easy – instructions

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Shimming the Vespa transmission made easy

In order to be able to adjust the sprocket free play on the main shaft you will need the corresponding transmission shims and two thickness gauges (you really need them twice) for measuring the transmission.

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It is best if you begin in first gear with a standard shoulder ring measuring 1.0mm so that later on when everything is mounted the gears firmly stay in place and you can properly shift the transmission into the neutral gear.

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Beginning below the first gear using a shoulder ring that is too thick could cause the gear selector cruciform to no longer be in a free position between the sprocket segments and make it want to engage the sprockets in the neutral.

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Therefore it is wise to first of all place the necessary shim behind the fourth gear. BGM6020 002

Checking the transmission free play

You can now check the sprockets‘ free play using the thickness gauges.

After mounting the parts the free play should range from 0.05mm to 0.15mm. In transmissions that entirely consist of new components you should rather opt for a tighter free play because the components have yet to “adapt to one another”. BGM6020 006

Do not choose too little free play

What you should not do either is overdoing it and allowing too little free play. This will result in the contrary of what you want on a running transmission. The hardened surfaces of the sprockets and shoulder rings tend to chew in, hence drastically increasing the free play within a short period.

If you want to replace individual sprockets of your transmission, we recommend that you order a set of shoulder rings ranging from 1.0mm to 1.3mm right away. And while you’re at it anyways, have a look at the gear selector cruciform. Do not try to save on transmission oil and replace it – and don’t forget to use new O-rings.

The right tools in good quality for your scooter will always help you do the job.

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Vespa BGM PRO transmission shims
BGM PRO shoulder rings

  • hardened and grounded parallely
  • just +0/-0.04mm tolerance
  • available in many thicknesses
  • for a precise gear change
  • and a long lasting gearbox
You get precise shifting here
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