Small primary gear -BGM PRO 25/65 (2.60) for BGM PRO primary gear- Vespa V50, PV125, ET3, PK50, PK80, PK125 - 25 tooth (straight teeth)

The BGM primary pinion shown here can only be used in combination with the matching BGM primary wheel. It can be used as a spare part or to adjust the gear ratio for the BGM PRO primary.

• The primary sprockets 19-20-21-22Z are suitable for the primary wheel 64Z

• The primary pinions 25-26 for the primary wheel with 65Z

By changing the primary pinion, which is only possible by disassembling the clutch cover, the primary gear ratio can be easily adapted to the needs.

Case study: An 85cc cylinder on a V50 is driven with a BGM primary 19/64 = 3.37. The cylinder is exchanged for a larger displacement 102cc cylinder. Afterwards, it is found that the larger displacement has greatly improved the pull, but the engine feels like it is over-revving, effectively missing fifth gear. Simply changing the primary pinion to, say, 21 teeth, extends the primary gear ratio to 2.90. The engine can now convert its increased torque much better, the gears can be extended further. At the same speed, the speed is higher, the final speed increases.