The bgm Pro Sport shift cross we have adapted to the increased requirements of today's engine concepts.
The inner values are decisive so that the shift cross ensures safe gear changes and driving pleasure for a long time.
The middle section (green) must ensure a secure attachment to the shift bolt and be sufficiently flexible so that no breaks can occur at this point under high loads. This zone 1 is tough-elastic in connection with the material used and a hardness of approx. 45HRC.
In Zone 2 (orange), in which the crossbar runs in the main shaft, the crossbar must still have tough elastic properties, but the surface must have greater hardness in order to withstand the wear in the (very hard) main shaft at this point.
The outer area (red) must be resistant to the impact load of the gear wheels when shifting. These areas mechanically engage the gear wheels. Great resistance to wear is required here. The remuneration takes place with up to 60HRC.
The hardened new bgm Pro Sport shift cross is a reliable companion for many kilometers with performance-oriented engine concepts.
In order to check whether the shift crosses can withstand extreme demands and whether the middle section is sufficiently flexible, we recorded a small test in the video.
The test method used is rather pragmatic, but has already shown in various tests that cross-shifters can also be too hard or too soft and deform significantly or even break here.
The new bgm Pro Sport shift cross is for PX 1982 to 2016 and PX/Rally/Sprint available
How often should a shift cross be changed?
In an original PX125 with approx. 7,5 hp on the crankshaft and moved in normal everyday life, a good shift cross can certainly make the normal maintenance interval of approx. 20.000km until the next engine overhaul without showing any significant losses in terms of function.
Of course, the wear and tear looks completely different if a transmission is operated with a Malossi MHR, 35 hp on the rear wheel and with a preference for mountainous country roads. Here the intervals until the next change of some engine components can be significantly shorter. Especially with a component that is subject to such high loads such as the gearshift cross and the engine mounts, the intervals until a component needs to be replaced are in the direction of 10.000 to 15.000 km.
The environment in which the shift cross works is also decisive for durability.
It is essential, for example, to correctly measure the gear wheels on the main shaft using the appropriate ones Shoulder rings
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. The gear "jumps" out.
Piaggio has specified a clearance of 0.1mm as the installation dimension. According to the Piaggio workshop manual, the shoulder rings of an original engine should be replaced if there is play of 0.55mm or more. From experience we can only advise to keep the play of the gear wheels on the main shaft as close as possible to the installation dimension of 0.1mm.
Heavily worn gear wheels with clearly rounded end faces of the segments also lead to increased wear of a shift cross. The shift cross can no longer hold properly on this convex surface and jumps out of gear.
So if you carry out an engine overhaul or want to change the shift cross, it is always important to look at all the other components and replace them if in doubt.
