Gearbox -BENELLI BULL-6- Vespa Smallframe - reinforced 5-speed gearbox up to 50 hp plus
The BULL-6 gearbox from Benelli is a reinforced, close-ratio 5-speed gearbox for Vespa Smallframe engines that has been specially developed for powerful setups. A specially designed shift claw and stable Benelli gears ensure clean shifting, high transmission reliability and significantly reduced wear - even in engines that are well over the 50 hp mark.
Benelli BULL-6
5-speed short layout
Complete gearbox with main shaft
For 50 hp plus setups
Design and concept
Benelli has specialized in reinforced Vespa transmissions for many years. The BULL-6 short 5-speed gearbox uses a shift claw specially developed for Vespa smallframe engines, which distributes the applied forces better and protects the gear teeth. In conjunction with the Benelli gears, the result is a package that offers a very high level of operational reliability both in sprint mode and on the racetrack - without completely losing sight of everyday practicality.
The gearbox is supplied as a pre-assembled unit, consisting of main shaft, gear cluster and matching gear claw. It is designed for Piaggio original cases and common aftermarket charters with standard dimensions. No housing modifications are required for installation, apart from the classic gearbox alignment. The standard small starter gear (z = 10) is still used.
Shift claw and gear layout
Gearshift claw specially developed for Vespa Smallframe, adapted to the 5-speed layout of the BULL-6.
Better support of load peaks when shifting and under full load, less local overload at the shifting edges.
Cleaner gear changes, less tendency for gears to jump out when engines are used hard.
Significantly reduced wear compared to conventional series components with the same or higher engine output.
Gear ratio and area of application
The BULL-6 Short is supplied as a completely pre-assembled unit including a reinforced main shaft and is matched with the following gear ratios:
- 1st gear: 10 - 57
- 2nd gear: 12 - 53
- 3rd gear: 15 - 52
- 4th gear: 17 - 49
- 5th gear: 19 - 46
The gears are deliberately close together ("short" gradation). This makes the transmission ideal for short and long-stroke smallframe engines that have little torque from the cellar but reach high rated speeds. Thanks to the narrow spread, the engine remains better in the usable power band when shifting up, which is particularly beneficial on winding roads and in racing.
In Italy, the transmission has already been tested in the most powerful classes of the IDC. Even engines that clearly exceed the 50 hp threshold are kept safely under control by the BULL-6 without any loss of shiftability.
Use in practice
Ideal for smallframe engines with greatly increased power, where standard gearboxes reach their mechanical limits.
Due to the narrow gradation, it is particularly suitable for high-revving short and long-stroke setups with comparatively little torque in the lower speed range.
Plug & play installation in Piaggio and common tuning engine housings with standard dimensions, no milling or welding required.
Completely pre-assembled unit significantly reduces the assembly effort compared to freely configured gearbox combinations.
Scope of delivery
- Complete BULL-6 Benelli 5-speed gearbox for Vespa Smallframe (short gearing)
- Reinforced main shaft pre-assembled
- Benelli gear wheels (5 gears) in short "Big Cruise" tuning
- Dedicated shift claw to match the 5-speed layout
FAQ: BULL-6 Benelli 5-speed gearbox Vespa Smallframe
Frequently asked questions
What engine power is the BULL-6 Short 5-speed gearbox designed for?
The gearbox was tested on engines that produce well over 50 hp. It is clearly designed for powerful smallframe setups and for engines where experience has shown that the standard transmission reaches its limits.
What advantages does the 5-speed downshift offer over a 4-speed gearbox?
The additional gear means that the overall spread can be kept smaller and the jumps between the gears narrower. Particularly with high-revving engines with little torque in the lower range, the engine remains better in the power band when shifting up, which improves acceleration and drivability.
Do I have to machine the engine case for installation?
No. The gearbox is designed for Piaggio Smallframe engine cases and common aftermarket carters with standard dimensions. No milling or welding is required - only the usual gearbox alignment has to be carried out and the standard starter gear (z = 10) is still used.
Is the BULL-6 Short 5-speed gearbox suitable for everyday use?
The set-up is designed to be sporty and narrow, but - in combination with a suitable primary gear ratio - it can certainly be ridden on engines suitable for touring. However, it is generally oversized for pure city scooters with standard performance.
Is the gearbox supplied as a kit or pre-assembled?
The BULL-6 Short comes as a completely pre-assembled unit including a reinforced main shaft and matched Benelli gears. This reduces the risk of assembly errors and facilitates installation in powerful smallframe engines.
DE | €
