2010 Yamaha YZ450F

The standard approach to improving handling is to concentrate the motorcycle's heaviest components at its centre in order to achieve mass centralisation. But using conventional packaging techniques, this method has reached its limit. So the YZ450F development team took an entirely new approach in order to raise the bar to a new industry standard.
Fuel injection is the key to unleashing the YZ450F's true potential. It has allowed the development team to try an innovative new layout, a rearward slanting engine with a straight intake tract mounted in a lightweight Bilateral Beam frame. To prove their theories, Yamaha engineers built a prototype featuring this new generation packaging. The result is a machine that truly reconfigures the MX landscape.
Yamaha is a renowned innovator having already developed Monocross suspension and the new wave of 4-stroke moto crossers. But despite being the first manufacturer to feature the system in prototype form, fuel injection has taken a relatively long time to be introduced on a production Yamaha MX bike. The reason is the desire to get it right first time. Replacing the carburettor with FI is a simple task. But the development team wanted to ensure that the whole machine was developed in synergy and that the advantages offered by fuel injection were maximised.
The development team used the design freedom made possible by FI to completely redesign the machine without compromise.

All new chassis
A new Bilateral Beam aluminium frame sits at the heart of the YZ450F development project. This is a similar concept to the YZ250F frame but the execution is very different. The 450F frame was developed using a new structural analysis method that gives a responsive ride quality. The frame consists of sixteen components and is made using a revolutionary new semi solid die-casting technology High Solid Die Casting, which allows complex shapes to be made stronger, while also ensuring more consistency with other parts.
Thanks to this new generation layout, both sides of the frame are more symmetrical, a characteristic which contributes significantly to overall chassis feeling. This gives a consistent response from the area around the steering head, in spite of the ever changing impacts and forces applied to the frame. Regardless of the impacts it is subjected to, the rigidity balance delivers a consistent feel. The result is a frame that gives the rider excellent control of the machine and a superb sense of handling.
Supporting this revolutionary frame is a new suspension system. Both front and rear suspension units have more capacity, and the front fork has a 10mm longer stroke. This new, long-stroke fork is tuned for high traction under a variety of riding conditions and offers precise damping, particularly on the initial part of the stroke. Even more remarkable is the fork's supple operation when entering a corner. The rear suspension offers smooth damping to help prevent the rear of the bike from kicking up.
By moving the air cleaner box to the front of the tank, the mounting points for the rear suspension and swingarm can be moved forward towards the centre of the chassis. The swingarm is also very symmetrical, contributing further to the YZ450F's stable handling qualities.
Back to the future
Engineers have always known that a straight intake tract delivers efficient cylinder filling. And being the heaviest part of a motorcycle, the position of the engine is critical to handling. To tackle these challenges, the YZ450F development team decided to reverse the locations for intake and exhaust and create an all new engine layout.
The air cleaner box is now located where the tank was, so the intake tract can have a straight shot into the cylinder head. To achieve the proper exhaust pipe length from the rearward-slanting cylinder, the pipe twists in a coil before reaching the silencer.
The rearward slanting cylinder with its downdraft intake offers other benefits in addition to improved intake efficiency. The most remarkable of these is how it upgrades the YZ450F's handling. One of the drawbacks of the 4-stroke engine is its comparatively heavy cylinder head. By slanting the cylinder rearwards, the engine's inertial mass is concentrated more towards the centre of the machine. The new layout also gave the engineers more freedom in locating the rear suspension.
The evolution in the bike's performance exceeded all expectations. When they tested their idea with a prototype machine the engineers realised how effective it was. As a result of its superior handling performance, the YZ450F is very stable during corner entry and corner exits, giving the bike a much lighter and more responsive feel. This allows the rider to open the throttle sooner and to keep it open longer. It is the synergy between engine and chassis that makes the YZ450F such a stellar performer.
Fuel injection has various other benefits, such as control over air/fuel mixtures in response to altitude and temperature changes. Also, a newly developed and easy to use plug-in FI setting tool is available as an aftermarket item. The YZ Power Tuner makes it easy for riders to adjust the fuel load and ignition map to suit their riding style and riding conditions.
Other benefits of the forward-mounted intake include cooler intake air because it is unheated by the engine, and cleaner air, because the dirt and dust kicked up by the rear tyre is further away from the intake system.

YZ450F main features
Engine features: Newly designed liquid-cooled 4-stroke, DOHC, single-cylinder 4-valve engine. The newly developed engine on this model is designed and engineered to provide power development characteristics that make for better drivability for a 450cc motocrosser while also contributing to better centralisation of machine mass.
Unique fuel injected engine design with straight intake and rearward-slanting cylinder.
A unique new fuel injected engine with straight intake and a rearward slanting cylinder has been developed.
This innovative new layout defies the accepted concepts of chassis design and has introduced a new dimension of drivability not possible in a chassis developed for carburettor fed engines.
Front straight intake: The front straight intake directs air from the intake ducts on the right and left sides of the inside of the front air duct through the air cleaner positioned inside the frame and into the intake port, thus achieving excellent intake efficiency while also contributing to better centralisation of machine mass.
Fuel injection that contributes to drivability: The fuel injection system is designed to make setting corrections to maintain optimum combustion demanded by a moto-crosser under changing running conditions, including changes in engine temperature, air temperature and air pressure. To monitor changes in running conditions, the system is equipped with a throttle position sensor (TPS), intake pressure, intake air temperature, air pressure, crankshaft rpm and coolant temperature sensors.
Based on the data from these sensors, the compact ECU calculates the optimum induction fuel volume to accommodate changing conditions. For the fuel supply system, a compact, lightweight motocross-specific fuel pump has been adopted along with simplified periphery parts to save weight.
Rear Exhaust: The exhaust system is a rear-positioned type that passes under the seat. By adding curves to the exhaust pipe between the exhaust port and the muffler, it has been possible to maintain an exhaust pipe length comparable with that of the existing model while achieving better centralisation of machine mass. A resonator has also been fitted inside the exhaust pipe to ensure sufficient silencing effect while also bringing out excellent torque characteristics.
Offset cylinder adopted: By offsetting the cylinder 12 mm from the centre of the crankshaft, it has been possible to reduce friction loss and contribute to better engine characteristics.
Normally, when combustion forces the piston downward, there is also a lateral force component that pushes the piston toward the cylinder wall, resulting in friction between the piston and the cylinder wall. However, by offsetting the piston in a way that minimises piston and connecting rod slant at the moment of greatest combustion force, friction loss can be decreased.
This measure is called an offset cylinder, and it makes more efficient use of the force created by combustion.
This marks the first time that an offset cylinder has been adopted on a Yamaha production off-road competition model.
Optimised oil tank shape: A dry sump with an oil tank in the crankcase has been adopted on this model since the 2006 model as a system that provides stable lubricating performance while also contributing to better centralisation of machine mass. For the 2010 model the oil tank volume has been kept the same but the shape has been changed to a vertically elongated type to minimise changes in the oil surface and promote air-liquid separation.
Lightweight parts introduced: For the head cover and clutch cover a heat resistant magnesium alloy has been used to reduce weight while achieving a high quality exterior look at the same time.
YZ Power Tuner FI setting tool accessory: A FI setting tool ‘YZ Power Tuner' has been developed as an option so the rider can adjust fuel injection volume and ignition timing to meet personal taste or course conditions.
Chassis features:
• New design aluminium frame adopted.
• Optimum use of a variety of types of aluminium.
• Rear shock absorber aligned on the machine's central axis.
• New design swingarm.
• Longer stroke front suspension in order to improve shock.
• New dimension fork brackets.
• New design flat seat.
• Under-seat fuel tank.
• Lightweight exterior parts newly adopted.
• New exterior white paint.