Vespa gear claw from bgm PRO | Test comparison info

New Vespa gear shift claw from bgm PRO for Vespa 4-speed gearboxes

Vespa gear claw -BGM PRO- ROUND, 4 gear, H = 50mm

Vespa gear shift claw bgm PRO precision work from high quality material

The bgm PRO Vespa shifting claw BGM6550 is made of 15CrMo5 (SCM415) chrome-molybdenum steel and the additional tempering of the high-quality material gives the flanks of the shift claw a very high resistance to wear and tear. The flanks are very tightly tolerated compared to the switching claws that are mostly available on the market. This results in accurate guidance in the grooves of the main shaft, which effectively prevents the shifting claw from locking / tilting under load.

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We have revised the setting for the four speed levels and now offer them following advantages:

GEAR 1-2

The locking profile of the first gear has been revised so that it can be inserted more easily. It is also possible to shift to second gear much faster. This is a nice feature, especially in racing, to keep the interruption in tractive power as short as possible.

GEAR 2-4

The locking profiles of the other gears have been revised so that the gears lock in much more precisely. The unpleasant jumping out of a gear under load, which is often a problem with already slightly worn transmission gears with conventional shift claws, is largely prevented. The BGM switching spring has a supporting effect. Their spring force is precisely matched and offers ideal conditions for a gearbox that can be shifted well with full engaging gears.

Suitable for Vespa PK gearboxes

The BGM Pro Vespa shift claw is made for the so-called PK transmission type. This is driven with the round type switching claw (length of 50mm (overall height)). Round type shift claw means that the pins that snap into the gear wheel are provided with a radius at the transition to the end of the arm.

Help: Identify the gearbox

The PK type can be recognized by the marking on the gear wheels. This always starts with a 42xx (= round switching claw with 50mm). The old type is identified by the number 37xx (= angular switching claw with 51mm)

exceptions

The PK transmission version was already in the last years of construction of the

V50 (V5A1T from No. 69444),
V50 Special (V5B3T from No. 94315),
V550 Elestart (V5B4T from No. 1514) and the
PV125 (VMA2T from No. 150203) and
ET3 (VMB1T from No. 8161) used.

The development of a new Vespa shift dog

Racing tests

To develop the Vespa gear shift claw we did some tests. For example, we used a claw on several scooters for an entire racing season.
In some cases, the vehicles have also experienced several long-distance races and races as part of the ESC over the course of the season.

Here is the comparison between a new BGM Vespa gearshift claw from the current series (left) and a BGM gearshift claw from the test series, which was used over a year in two ESC classes and in long-distance races.

Permanently great switching behavior and low wear

The permanently good switching behavior and the low wear are of course partly due to the selection of the material and its compensation and partly to the precise guidance of the switching claw in the main shaft.

Precise manufacturing for this component is essential, but extremely complex. Some manufacturers on the market have therefore apparently decided to simply design the arms of the shift claw and thus the guides in the main shaft very generously - so the component no longer has to be manufactured so precisely in the end.

As a daunting example, we looked at a new, current Piaggio shift claw.

The surface quality of the original part is more than poor these days ...

The new bgm PRO Vespa shifting claw in comparison

On the left side again a BGM gearshift from the current series and on the right a new (!) Gearshift claw from the Piaggio bag

What is already indicated visually is revealed exactly when measuring.

Piaggio sets its own standards here ...

At 0.8mm, the backlash is clearly too big. Such a pawl inevitably leads to the gears jumping out under load.

The greater the backlash, the faster the shift dog can wear out. If the gap in the groove of the main shaft is too large, the shift pawl hits the main shaft with every load change and shifting process. The rather soft material of the simple shift claws suffers greatly from this load and wear increases further.

As a comparison, common Vespa shift claws available on the market have a backlash in the range of 0,4mm.
But here, too, there are outliers - even high-priced models from Italy stand out with around 0,7mm.

With the BGM switching claw, a meticulous tolerance of the backlash as small as possible held.

At just five hundredths, the backlash measures just as much as a human hair and the shift claw literally fits a hair's breadth perfectly into the main shaft.

Clean gear changes with the bgm PRO Vespa shift claw BGM6550

In conjunction with the Switching spring BGM PRO, crisp and precise gear changes are possible. The reinforced switch spring ensures that the switch balls lock securely into the setting.
The reinforced spring also prevents the gears from jumping out or the shift pawl from being pushed out of the engaged gear, even under load with increased gear play.

Order a Vespa gearshift claw