BGM PRO complete gearbox for Vespa Smallframe & PK scooters.

Manufactured in Europe from high-alloy NiCrMo case-hardened steel (14NiCrMo13) and hardened by Thyssenkrupp, it is designed to handle extreme loads. Independent tests show a 90% higher load capacity than original Piaggio gears, with a surface hardness of 58–60HRC for excellent wear resistance.

Suitable for both touring and racing. Gear ratios match the original Piaggio setup. Compatible with all common secondary shafts approved for use with stock gearbox parts.

The BGM PRO gearbox is Based on Piaggio’s later gearbox design introduced from 1976 onwards (commonly known as the PK gearbox). Used in ET3 and V50 Special models, these gears are marked with “42 … /s”. bgm PRO gears follow the same specification and are also marked “42”.

Fitment:
-Direct fit for engines originally equipped with this gearbox type or already converted to it.
-Pre-1976 engines can be upgraded without replacing the main shaft, requiring only bgm gears and a PK-type selector cruciform (50mm).
-3-speed engines can be converted to 4-speed using the correct cruciform (50mm) and bgm gears.
-Austrian-market models with a longer secondary ratio can also be converted if the secondary shaft is replaced.

Please note: Not suitable for Vespa V50 1st series (V5A1T with V5A1M engine up to no. 92876), as these have narrower cases and shafts.

Final gear teeth: 58t, 54t, 50t & 46t

The BGM PRO driveshaft is supplied ready for installation; fully assembled with gear cogs & cruciform, accurately shimmed & circlips fitted. It is paired with a BGM PRO auxiliary shaft to create the complete Vespa gearbox.

Available in three versions to suit different riding styles:
Standard: (10–14–18–22): Matches the original Piaggio gearbox, ideal for touring or stock-style setups.

Original: (10–14–18–21): Shorter 4th gear for sportier engines, keeping the revs in the powerband.

Sport: (10–14–17–20): Shorter 3rd and 4th gears, perfect for high-revving engines and racing use.

A hardened clutch nut is included with the auxiliary shaft.

A hardened Kickstart sprocket is also included (12/10t, 20.5mm ID)

BGM BGM0151ORI, BGM0151SPO, BGM0151TOU