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

Maximum stability with best performance by ideal graduations

Modern cylinders like Malossi MHR, Quattrini M244 or Pinasco 251 have raised the power and torque level of the Vespa Largeframe engines to a completely 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) allows a maximum load transmission (high motor torque), the very good toughness (ductility) a very high resistance to load peaks. The final 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: 12-13-17-20 (short fourth gear)
BGM6506: 12-13-16-19 (short third, extra short fourth gear)

	1st gear	2nd gear	3rd gear	4th gear
Original PX200	12/57	13/42	17/38	21/35
BGM 6504	12/57	13/42	17/38	21/35
BGM 6505	12/57	13/42	17/38	20/35
BGM 6506	12/57	13/42	16/38	19/35

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 on the 35 tooth wheel of the 200cc models.

BGM6505: 12-13-17-20 (short fourth gear)
To get a better gear connection between third and fourth gear and at the same time maximum stability, we recommend the use of 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 which is again a little bit shorter than with the pairing 21/36 (approx. 2-3km/h) with at the same time strongly 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, the gear jump from three to four still remains exactly suitable.

BGM6506: 12-13-16-19 (short third gear, extra short fourth gear)
The auxiliary shaft with 12-13-16-19 teeth represents a further expansion stage. 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.

ACCESSORIES
As an ideal combination for a powerful engine we recommend the clutch and primary parts of BGM PRO which are perfectly matched to the gearbox. 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 they are nevertheless not louder than the helical geared parts. Likewise, the springs of the primary internal jerk damping are adapted to the high torques. The tighter springs prevent the jerk damping from going 'on block', effectively keeping peak loads away from the gearbox. The BGM PRO auxiliary shafts are designed for use with BGM PRO or original Piaggio gears. The BGM PRO auxiliary shafts are designed for use with BGM PRO or original Piaggio gears.

Vespa Gearbox & Transmission*