The BGM PRO Torquemaster secondary shafts are an advanced version of the proven BGM PRO secondary shafts for Vespa large-frame transmissions. All three variants can be installed just like the corresponding original Piaggio part. No modifications to the engine housing, the shift mechanism, or the gear wheels are required.
1:1 replacement for Piaggio
No modifications
14NiCrMo13
58–60 HRC
three sizes
Direct replacement without modification
The dimensions, bearing locations, and gear positions correspond to the intended Piaggio transmission design. An existing secondary shaft can therefore be directly replaced with the appropriate Torquemaster variant. Additional spacers, special bearings, or modifications to the engine housing are not necessary.
Installation and Compatibility
Direct 1:1 replacement for the corresponding original Piaggio auxiliary shaft
No machining of the engine housing required
No modifications to the shift fork, gear wheels, or kickstarter mechanism required
Compatible with all standard Vespa large-frame gear wheels
Exception for BGM6515: Do not use a gear with more than 35 teeth in fourth gear
Three variants for different engine characteristics
The three variants differ exclusively in the tooth profiles of the third and fourth gears. The first and second gears correspond to the PX200 specification across all versions. This allows you to specifically choose how close the gear ratios should be in the higher range.
Variant Overview
| Item |
Gear Ratio |
Character |
Typical Application |
| BGM6514 |
12-13-17-21 |
Same as PX200 Series |
Touring engines and setups where the original 200-series gear ratio is to be retained |
| BGM6515 |
12-13-16-19 |
Short third gear, extra-short fourth gear |
Long primary ratios or high-rpm engines with close gear ratios |
| BGM6516 |
12-13-17-20 |
Short fourth gear |
High-torque engines with a wide power band and improved transition from third to fourth |
Direct comparison of gear ratios
The table shows the combination with the gear wheels of the PX200 transmission. Values that differ from the standard PX200 gear ratios are highlighted in bold.
| Transmission |
1st gear |
2nd gear |
3rd gear |
4th gear |
| Original PX200 |
12/57 |
13/42 |
17/38 |
21/35 |
| BGM6514 |
12/57 |
13/42 |
17/38 |
21/35 |
| BGM6515 |
12/57 |
13/42 |
16/38 |
19/35 |
| BGM6516 |
12/57 |
13/42 |
17/38 |
20/35 |
Comparison of RPM and Speed
The charts show the theoretical speed in third and fourth gears. The calculations are based on a PX200 primary gear ratio of 23/65 and an assumed rolling circumference of 1.34 m for a 3.50-10 tire.
Third gear
BGM6514 and BGM6516: 17/38
BGM6515: 16/38
Fourth gear
BGM6514: 21/35
BGM6516: 20/35
BGM6515: 19/35
These values are calculated for comparison purposes only. Tire brand, actual rolling circumference, and a different primary gear ratio will affect the actual speed.
Speeds in a table
| Variant |
Gear |
6,000 rpm |
7,000 rpm |
8,000 rpm |
9,000 rpm |
| BGM6514 |
3rd gear 17/38 |
76.4 km/h |
89.1 km/h |
101.8 km/h |
114.5 km/h |
| BGM6515 |
3rd gear 16/38 |
71.9 km/h |
83.9 km/h |
95.8 km/h |
107.8 km/h |
| BGM6516 |
3rd gear 17/38 |
76.4 km/h |
89.1 km/h |
101.8 km/h |
114.5 km/h |
| BGM6514 |
4th gear 21/35 |
102.4 km/h |
119.5 km/h |
136.6 km/h |
153.6 km/h |
| BGM6515 |
4th gear 19/35 |
92.7 km/h |
108.1 km/h |
123.6 km/h |
139.0 km/h |
| BGM6516 |
4th gear 20/35 |
97.5 km/h |
113.8 km/h |
130.1 km/h |
146.3 km/h |
Calculation basis: Primary 23/65, tire circumference 1.34 m.
Stability Through Proper Gear Pairing
With the same center distance, the individual teeth become wider when the gear pair has fewer teeth. This increases the load-bearing surface of the tooth flanks. Therefore, a short gear ratio achieved via a properly stepped secondary shaft is often more practical for high torques than a particularly large gear.
Note regarding the BGM6515 with 19 teeth in fourth gear
The ultra-short BGM6515 secondary shaft may only be combined with gear wheels having a maximum of 35 teeth in fourth gear. Gear wheels with 36 or more teeth are not intended for use with this secondary shaft.
BGM6514: Gear ratios identical to the PX200 series
With 12-13-17-21, the BGM6514 has exactly the same gear ratio as the standard PX200 transmission. It is suitable for engines where the proven Piaggio gear connections are to remain unchanged. Installation on an existing Piaggio auxiliary shaft requires no further modifications.
BGM6515: Short third gear and extra-short fourth gear
The BGM6515, with gear ratios of 12-13-16-19, significantly condenses the upper gear range. The shorter third gear reduces the RPM jump from second to third gear. The even shorter fourth gear keeps high-rpm engines closer to their power band when shifting up.
This gear ratio configuration is also suitable for very long primary gear ratios, such as 25/62. The first two gears remain usable for a long time, while the third and fourth gears follow each other more closely.
BGM6516: Short fourth gear
The BGM6516 with 12-13-17-20 retains the first through third gears of the PX200 standard gear ratio and shortens only the fourth gear. This makes it a very balanced solution for high-torque engines that use a long primary gear ratio but should not drop too far in RPM when shifting from third to fourth gear.
When combined with a 35-tooth gear, this creates the 20/35 gear pair. It offers a shorter fourth gear while also providing wide, durable gear flanks.
Material and Heat Treatment
The Torquemaster secondary shafts are made of 14NiCrMo13, material number 1.6657. The case-hardened steel combines a hard, wear-resistant surface with a tough core. This allows the tooth flanks to withstand high contact forces, while the base body remains structurally sound even under severe load cycling.
Technical Specifications
Material: 14NiCrMo13 / 1.6657
Process: Case hardening
Heat treatment: at ThyssenKrupp
Surface hardness: 58–60 HRC
Core: tough and strong enough to withstand high bending and cyclic loading
Design: for motors rated at over 30 PS and more than 35 Nm
Gear Compatibility
Torquemaster secondary shafts are not limited to BGM sprockets. They can be combined with all standard sprockets compatible with the respective Vespa Largeframe transmission design. This includes original Piaggio sprockets as well as compatible aftermarket parts from other manufacturers.
Overview
BGM6514: compatible with all standard, compatible sprockets
BGM6516: Can be combined with all common compatible gear sprockets
BGM6515: Also freely combinable, but in fourth gear only with sprockets up to a maximum of 35 teeth
Installation
Installation is the same as replacing an original secondary shaft. As with any transmission rebuild, the gear wheels, shift fork, retaining ring, and spacer washers must be inspected. The axial transmission play must be adjusted according to the manufacturer’s specifications.
Remove the existing Piaggio countershaft
Install the Torquemaster secondary shaft without modifying the housing
Inspect the gear wheels for damage and worn shift surfaces
Use a compatible shift fork
Adjust the transmission play using suitable spacer washers
Check the kickstarter sprocket and kickstarter segment for wear
Conclusion
The BGM PRO Torquemaster secondary shafts replace the corresponding original Piaggio secondary shaft without requiring any additional modifications. The BGM6514 retains the stock gear ratios, the BGM6516 specifically shortens fourth gear, and the BGM6515 offers a short third gear and an extra-short fourth gear. This allows you to select the gear ratios to match the engine’s characteristics, primary ratio, and desired RPM range.
FAQ
Yes. All three Torquemaster variants are designed as direct 1:1 replacements for the corresponding Piaggio part. No modifications to the engine case or the shift mechanism are necessary.
BGM6514 corresponds to the PX200 standard gear ratios. BGM6516 shortens only the fourth gear and is well-suited for high-torque engines. BGM6515 features a short third gear and an extra-short fourth gear for long primary ratios or high-rpm engines.
Yes. The secondary shafts can be combined with all standard, compatible large-frame gear sprockets. This applies to original Piaggio gear sprockets as well as suitable aftermarket parts.
Yes. The BGM6515 has a 19-tooth pinion in fourth gear. Only a fourth gear sprocket with a maximum of 35 teeth may be used here. Gear sprockets with 36 or more teeth are not approved.
The shorter tooth pitch of the auxiliary shaft allows for the continued use of a stable 35-tooth gear. This results in better gear meshing and wide tooth flanks for high torques.
Torquemaster auxiliary shafts are designed for high-performance Vespa large-frame engines with over 30 PS and more than 35 Nm of torque. They can also be used in stock-based and touring-oriented engines.
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