Shaft BGM PRO for Vespa Largeframe PX, Rally, T5, Cosa, LML (2-stroke)

Modern cylinders like Malossi MHR, Quattrini M244 or Pinasco 251 have raised the power and torque level of Vespa Largeframe engines to a whole new level.
The transmission components used must be correspondingly stable.

MATERIAL QUALITY
The BGM PRO auxiliary shafts are made of high-quality 21NiCrMo2 (1.6523) case-hardened steel whose surface is finally hardened and tempered to 62HRC. The high core strength of the material (900N/mm²) enables maximum load transmission (high engine torque), while the very good toughness (ductility) enables very high resistance to peak loads. The final tempering (heat treatment) hardens the surface to a depth of 0.6-0.8mm resulting in maximum wear protection.

• MATERIAL: 21NiCrMo2 (1.6523)

• HARDNESS: 62HRC

• GRADATIONS GEAR 1-4:

• BGM6504: 12-13-17-21 (standard gradation)

• BGM6505: 12-13-16-19 (short third, extra short fourth gear)

• BGM6506: 12-13-17-20 (short fourth gear)

MAXIMUM STABILITY THROUGH CORRECT TRANSMISSION DISTRIBUTION
In addition to perfect adaptation of the transmission to the engine characteristics, the gradation of the auxiliary shaft has another important aspect.
The fewer teeth a gear pair has at the same center distance, the more stable it is (the teeth become wider).
For this reason, a `short` fourth gear with 36 teeth (original only on 125cc!) should not be used on an engine with a high torque, for example. Here the tooth flanks are less wide than with the 35 teeth wheel of the 200cc models.

BGM6505: 12-13-16-19 (short third, extra short fourth gear)
A further stage of development is the auxiliary shaft with 12-13-16-19 teeth. Here the third gear is also one tooth, the fourth gear already two teeth `shorter`. Thus the gear jumps of 2-3 and 3-4 are clearly shorter than with the factory tuning of Piaggio. This is ideal if a very long primary reduction (e.g. BGM 25/62) is to be used in a high-torque engine or if the engine is very rev-heavy and a short gear step is needed to always stay within the engine`s power band.

BGM6506: 12-13-17-20 (short fourth gear)
To still get a better gear connection between third and fourth gear while maintaining maximum stability, we recommend using the auxiliary shaft with 12-13-17-20 gradation. Here the auxiliary shaft for the fourth gear has one tooth less (20Z instead of 21Z = more stable) and can therefore be combined with the original fourth gear of the 200cc models with 35 teeth (= more stable). As a result, you have a fourth gear that is again slightly shorter than with the pairing 21/36 (about 2-3km / h) at the same time greatly increased load capacity. This auxiliary shaft is therefore ideal for engines with a lot of torque and a linear power curve. The motor can then be reduced sufficiently long on the primary side, while the gear step from three to four still remains exactly suitable.

ACCESSORIES
As an ideal combination for a powerful engine, we recommend the clutch and primary parts from BGM PRO, which are perfectly matched to the transmission. For powerful engines, we exclusively recommend the use of straight-toothed clutch and primary drives. These are constructively up to the high loads and due to their careful manufacturing nevertheless not louder than the helical toothed gearbox parts. Similarly, the springs of the primary internal jerk damping are adapted to the high torques. The tighter springs prevent the shock absorber from going `on block`, effectively keeping peak loads away from the transmission.The BGM PRO slave shafts are designed for use with BGM PRO or original Piaggio gears The BGM PRO slave shafts are designed for use with BGM PRO or original Piaggio gears.

(US)