The Roadson BT550 Superleggera

Only 97 kg 'wet' (including oil and water), this 550cc 4-stroke v-twin race bike has been developed by French specialists Roadson, formerly known as 'Tuscon' (it's a long story involving corporate lawyers).

As you may have guessed already, this little beauty is powered by Aprilia's extremely light and compact 77° v-twin. This engine has seen great success on their multi-championship winning RXV motocross bikes.

77° V twin four-stroke. Liquid cooled. Single overhead cam with rocker operated exhaust valves. 4 valve heads with titanium valves.

In my opinion this is the best 4-stroke motorcycle engine ever made. At 33kg, 42 cm long, 43 high, 29 wide, and 70 hp it is the perfect compromise between weight, complexity, size and horsepower. So it is a pity that nobody has had the foresight to make use of it in a road legal, superlight sportsbike. I guess that Aprilia are simply not interested in undermining their high profit, but unusable, hyper-bikes by producing a small capacity sports bike at half the cost that is more fun to ride and would spank any large capacity superbike on a winding road (end of rant).

Kudos then to engineer and owner Jeff Robert and the team at Bako Design for seeing the potential of exploiting such a compact engine. They have created a racer with 125 GP dimensions that is quick enough to compete against much more powerful Ducati and Aprilia superbikes the pro-twins race series.



Jeff Robert:

"We have used the fact the the rear cylinder is not in the middle of the bike, but on the right side to place here the rear suspension. The front the cylinder is on the left, (because the 2 connecting rods are side by side). [Here] we used the free [space] to put the battery. So most of the weight (engine battery and shocks) is in the center of the bike. We also put the tank under the [rider]."

"Tires are another cornerstone of our project. With narrow (125 GP) tires, we reduce the frontal area and therefore drag. But that's not all. They reduce the rotating mass and gyroscopic effect. Mounted on narrow and lightweight wheels, they help improve maneuverability and acceleration of the bike."