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.
An overhead camshaft operates the four valves (titanium intake valves) by means of weight-optimized rocker arms and also serves as a centrifuge for the engine ventilation. In comparison to the previous model, minimized oscillating masses, larger valve cross-sections and a shallower valve angle lead to noticeably increased performance and improved rideability in the lower load range. A magnesium cylinder head cover that is set at an angle makes maintenance much easier.
Though not the first off-road bike to feature EFI (Electronic Fuel Injection is already standard on ATK, Gas Gas and Sherco models and Suzuki will be the first Japanese manufacturer to offer EFI on a dirt bike in 2008 on the RM450 motocross machine), the Husaberg is certainly running 21st century technology and riders of the Husaberg can expect a cleaner throttle response, better mid-range and top end power and much better fuel consumption, not to mention less emissions and less fiddling getting the jetting just right .
The Keihin engine management system uses a 42-mm throttle body in a direct downdraught from the airbox which is positioned within the fuel tank - this means optimum air-flow and therefore maximum performance. Other advantages of a computer-controlled fuel-air mix include an automatic choke, temperature and height compensation and more riding, less fiddling and instant starting, which can be an absolute life-saver if you manage to stall on a hill. Throw in the electric starter and life will be much easier on the Husaberg than with the ankle-breaking, lung-busting starting techniques required from the performance thumpers of not long ago. Indeed, the Husaberg has completely done away with a kick-start lever. Old-timers might eye this with suspicion, but … we doubt they’d lose the kick-starter if they weren’t confident.
A positive displacement pump reliably supplies oil for all the essential components, such as the crankshaft, pistons and valve train, while a suction pump draws excess oil out of the cylinder head and sends it back to the transmission. And now that there’s only one oil filter, maintenance is easier.
The clutch is designed for extreme loads, with an integrated cush drive and increased oil supply. The system also receives top marks for precise application, thanks to the new Magura hydraulic clutch operation.
In conjunction with an ultra-modern chassis design, it has created an enduro bike that sets a brand-new benchmark for innovative technology and offroad handling.
The new engine concept also breaks the mould when it comes to the chassis. The highest priorities for the Husaberg engineers were: a weight distribution that facilitates handling, the incorporation of high-quality components, the lowest possible weight and super-sporty bodywork with enduro-ready ergonomics.
A new chrome molybdenum frame with a perimeter design ensures the greatest torsional rigidity and reliable tracking stability at a minimum weight. Due to the upright design of the engine, the tubes that pass beneath it were given an extremely slender construction and drawn further toward the back. That allows the bike to have the narrowest overall width and more ground clearance – a huge advantage in difficult terrain.
Further breaking with tradition, many dirt riders will be amazed to find that the subframe is made of cross-linked polyethylene (PEX). In addition to reduced weight and increased rigidity, this material offers a free choice of shape. This means that numerous electric components can be safely installed in the back of the bike, and an opening in the side beneath the seat acts as a handle, so the rider can come to grips with the bike in rough terrain.
Shaped to follow the bending moment, the die-cast swingarm is connected to the directly linked PDS shock and is constructed so that both arms exhibit the same flex properties. This apparently provides the greatest tracking stability and plenty of traction and comfort.
The fully adjustable, 48-mm upside-down forks from WP Suspension guarantee sensitive responsiveness and high damping reserves. Thanks to their broad set-up range, the forks can be ideally adjusted for the riding surface and rider. The CNC-machined triple clamps guarantee the greatest steering precision and stability.
The fully adjustable PDS shock from WP with a lightweight, aluminum reservoir tube features adjustable rebound damping plus adjustable high and low-speed compression damping, so it can be perfectly regulated for the most diverse conditions.
The newly developed front wheel brake comes from Italian specialists Brembo, featuring a new, lighter, floating caliper and smaller pistons, provides maximum yet properly applied braking power with a minimum of effort. At the rear, a single-piston brake caliper gets a grip on the ultra-light brake disc with wave design.
The exhaust manifold was integrated into the bike so that it’s well protected from rock damage and so that the rider doesn’t come into contact with it either. The beautifully shaped and lightweight aluminum silencer definitely complies with the mandatory noise limits.
An 8.5-litre fuel tank of transparent polyethylene that extends far beneath the seat helps keep the bike’s centre of gravity as low as possible. The compact fuel pump is situated toward the bottom, while the airbox is situated right behind the tank cap – an advantageous position for the intake of cool and clean air, as well as for maximum fording depth. The slender tank design offers optimum freedom of movement and sporty ergonomics.
New plastic parts and modern in-mold technology for the spoilers underscore the trend-setting appearance of the entire motorcycle. Technical Specifications - Husaberg 450 FE
- Engine 1-cylinder 4-stroke SOHC
- Displacement 448.6 cc
- Bore/Stroke 95/63.4 mm
- Compression Ratio 11.9:1
- Control 4 valves
- Starter/Battery Electric starter only, 6 Ah
- Transmission 6-speed Enduro
- Carburation Keihin EMS with EFI
- Engine Lubrication Pressure lubrication with 2 pumps
- Clutch Wet clutch, Magura hydr. activation
- Frame Perimeter chrome-moly
- Subframe Cross-linked polyethylene
- Handlebars Tapered aluminum
- Front Suspension WP USD 48, open cartridge
- Rear Suspension WP PDS 5018 DCC
- Suspension Travel Front 300 mm, rear 335 mm
- Brakes Front/Rear Brembo
- Rims Front/Rear 1.60 x 21"; 2.15 x 18" Excel
- Tires Front/Rear 90/90-21"; 140/80-18“
- Main Silencer Aluminum
- Rake 63.5°
- Wheelbase 1.470±10 mm
- Ground Clearance 390 mm
- Seat Height 930 mm
- Fuel Capacity 8.5 l
- Weight 112 kg