Husaberg redesigns the four-stroke single
January 14, 2008 The development of the four-stroke single cylinder motor is exactly as old as the internal combustion engine, but the needs of the motorcycle are still being understood. Accordingly, Husaberg’s radical new design just might be a significant breakthrough. The engine has been reconfigured to put the crankshaft near the off-roader’s center-of-mass and the KTM-owned company claims a significant improvement in handling because of it.
Husaberg is just 20 years old, having been born from the sale of Swedish motorcycle brand Husqvarna to Italian company Cagiva – a team of Husqvarna engineers chose instead to start a new company and embarked on a tradition of radical innovation based around four-stroke powerplants.
The company’s first motorcycle set the scene – muscling a motorcycle at speed in off-road conditions is about as physically demanding as sport gets and the company adopted an entirely logical approach to dirt bike design focused on radical weight reduction and a commitment to centralizing weight at the center-of-mass, much the same as pioneer Erik Buell has done with road bike design.
While Buell accomplished remarkable handling improvements with road bikes, Husaberg was one of the key players in promoting the new breed of off-road four-strokes which are radically improved compared to the four-strokes of a quarter century ago – the broad but modest power delivery of the overweight four-strokes has now been matched by dramatically lighter weight, resulting in machines that are much easier to ride.
Now a KTM-subsidiary, Husaberg is about to embark on an even more radical solution to centralizing mass, completely reconfiguring the four-stroke motor for its next generation of machinery which we’ll see from mid-2008 as 2009 models.
The 2009 Husabergs will use 448.6 or 565 cc SOHC (single overhead camshaft) engines with a radical design and a new flat, 70° cylinder angle, fed by electronic fuel injection.
The developers’ goal was to position the crankshaft near the overall center of gravity, where the gyroscopic forces it generates have least effect on the handling of the bike. In this position, the gyroscopic forces generated by the rotating crankshaft have the lowest possible leverage effect on the bike, which is claimed to result in exceptionally good handling for a four-stroke, single-cylinder.
The shallow cylinder angle of 70° enables the crankshaft to be repositioned more than 100 mm higher and 160 mm further back, which moves the crankshaft’s rotating masses closer to the motorcycle’s center of gravity.
For enduro riding, there are some quite favorable side-effects of the lifted engine – the engine is narrower and has much improved ground clearance – an enormous advantage in narrow, rocky terrain