The BGM primary sprocket 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 pinions 19-20-21-22T are suitable for the 64T primary wheel
The primary pinions 25-26 for the 65T primary wheel
By replacing the primary pinion, which is only possible by removing the clutch cover, the primary gear ratio can be easily adjusted to suit requirements.
Case study: An 85cc cylinder on a V50 is ridden with a BGM primary 19/64 = 3.37. The cylinder is replaced with a larger displacement 102cc cylinder. Afterwards it is noticed that the larger displacement has greatly improved the pulling power, but the engine feels as if it is over-revving, the fifth gear is virtually missing. Simply changing the primary pinion to 21 teeth, for example, extends the primary reduction ratio to 2.90. The engine can now convert its increased torque much better and the gears can be extended further. At the same engine speed, the speed is higher and the top speed increases.
