The inner values are crucial to ensure that the gearshift cross provides reliable gear changes and riding enjoyment for a long time. The middle section (green) must ensure secure attachment to the shift bolt and be sufficiently flexible to prevent breakage at this point under high loads. This zone 1 is kept tough and elastic in connection with the material used and a hardness of approx. 45HRC. In zone 2 (orange), in which the shift cross runs in the main shaft, the shift cross must still have tough elastic properties but the surface must have a greater hardness in order to resist wear in the (very hard) main shaft at this point. The outer area (red) must be resistant to the impact load of the gears during the shifting process. These areas engage mechanically with the gears. High resistance to wear is required here. The hardening takes place at up to 60HRC. The new bgm Pro Sport gearshift clutch equipped in this way is a reliable companion for many kilometers with performance-oriented engine concepts.
In order to check whether the gearshift crosses can withstand extreme demands and whether the middle section is sufficiently flexible, we have recorded a short test in the video. The test method used is rather pragmatic, but has already shown in various tests that gearshift crosses can also be too hard or too soft and deform significantly or even break.The new bgm Pro Sport gearshift cross is available for PX 1982 to 2016 and PX / Rally / Sprint
PX 1982 to 2016PX / Rally / SprintFor example, it is essential to correctly calibrate the gears on the main shaft using the appropriate
Shoulder rings transmission shims bgm PRO for Vespa and Lambretta
Click!If the axial play of the gear wheels on the main shaft is too large, the gear wheels on the main shaft can tilt and wobble and thus move the shift cross out of the respective gear wheel. Piaggio has specified a play of 0.1 mm as the installation dimension. According to the Piaggio workshop manual, the shoulder rings on an original engine should be replaced when the play reaches 0.55 mm. Based on our experience, we can only advise you to keep the play of the gears on the main shaft as close as possible to the installation dimension of 0.1mm.
Heavily worn gears with clearly rounded end faces of the segments also lead to increased wear of a gearshift cross. On this crowned surface, the gearshift cross can no longer hold properly and jumps out of gear. So if you are carrying out an engine overhaul or want to change the gearshift cross, it is always important to look at all other components and replace them if in doubt. 