Revolutionary. It’s a word associated with new motorcycles all too often these days, but when Yamaha Moto Australia’s Sean Goldhawk told us that the 2010 model Yamaha YZ450F was revolutionary, rather than evolutionary, I believed him.

Just one look at the new bike and you’ll see it’s hugely revised. In fact, it’s so different that Yamaha classes the bike as being just as revolutionary as its YZ400F from 1998 – the first modern four-stroke motocross race bike.

That one claim makes you stand up and realise just how much effort and thought has been put into the development process for the 450 of 2010, and as you’ll see below in the tech info, the list of technical changes and advancements is very long.

There’s no doubt that four-strokes are here to stay, and mass centralisation has long been the aim of the manufacturers in order to produce a bike that handles the best it possibly can.

Well, Yamaha felt that it couldn’t centralise the mass any further in the previous guise, so in taking advantage of the lack of a carburettor in switching to fuel-injection, the bold new YZ450F is radically different in so many ways as you can see further down the page.

And the result? One heckuva brilliant motorcycle, admired by all and ridden with confidence by many at the Australian media launch on the new track at Appin – home of the Macarthur District Motorcycle Club in New South Wales.

On a new track prepared, ripped and watered specially for the launch of the most revolutionary (there’s that word again) motocross bike of the new year, Yamaha engineers can stand proud in their development of the new fo-fitty.

First of all, it’s completely different than I had envisioned. What looks to be a relatively large bike when observing it, almost feels like a Lites class weapon honed and ready for battle.

As current double Australian Pro Open Motocross Champion Jay Marmont explained before we got out on track, everything just seems to fit nicely in its position. The new flat seat perches you over the front, which assists in turning prowess, while the relationship between the handlebars, foot pegs, and seating position makes moving around on the bike a cinch whether you’re large or small.

The quality of the bike is unquestionably high and does admittedly take some time to get used to when you first lay eyes on it, with so many things back-to-front due to the unique engine configuration.

Its styling is similar to the new YZ250F, but visually looks bulkier, signifying that it’s the high-capacity 450 that you’re casting your eyes on.

Power is simply sensational on the new Yamaha Open class bike, with fuelling next to perfect as you’d expect from a bike with EFI, coming on in an instant when the throttle is twisted and remaining smooth throughout the powerband.

What’s amazing in the whole deal is the difference that the YZ Power Tuner makes when you slot a new map into the EFI system, with Yamaha having nine pre-set for us to put through their paces on the day.

Proving easy to use after a bit of troubleshooting, riders or mechanics can adjust the settings on the fly in between races without any need for a laptop computer or any of the kind.

The standard setting offers a smooth power that is quite easy to control, essentially offering a medium range of power in the bottom-end all the way to the top-end as you’re hard on the gas.

A number of maps were developed by Marmont on the same circuit two days earlier, with a “Jay Marmont Race” setting proving to be my favourite for the day on that particular track.

Even smoother off the bottom offering a tractable range of power, Jay’s setting really kicked in throughout the mid-range and was an absolute weapon on the top, although it’s clear that he takes advantage of that better than most!

A “Jay Marmont Traction” setting was also favoured for me with a revised setting that was slightly more abrupt off the bottom with more torque, while a “Clubman Race” setting felt that touch more torquier.

The impressive thing is, just plugging the YZ Power Tuner in can change the power in no time, completely converting the characteristics of the engine and being fully-adjustable if you’d like to place your own settings into it. Cool!

On Jay’s race setting it feels like the engine isn’t going to stop pulling, and it’s surprisingly user-friendly considering it’s a map developed by Jay – showing that he likes a smooth, broad delivery of power capable of high top speeds.

You can partially twist the throttle in search of traction on the soft Appin bulldust, twist it more and enjoy the response, and then once you’re out of the corner a handful of gas won’t fail to impress.

It’s easy to start hot or cold, basically taking it to top-dead-centre and leveraging down on the kick-starter and firing up on the first kick most of the time if you perfect the technique.

The power really is a broad range, impressive in the many adjustments you can tap into it, and realistically having more power than I could ever make the most of. In saying that, ride it at your limits and it will play nicely with you.

It sounds trick, too. Quick bursts of power cause a pingy bark out the twisty exhaust, not too dissimilar to those heard every Saturday night lately at the Super X rounds – seriously.

The six-speed gearbox is light and easy to shift, with an equally light clutch feel adding to the overall quality of the ride as you’re working it around the track negotiating the obstacles.

Yamaha states in its press kit that the handling is greatly improved due to the arrangement of the rearward-slanting engine and all of the components surrounding it, and I wouldn’t disagree.

To be honest, it’s incredible when I think back to the first 400. Yamaha has continued to push the boundaries over the years, with champions such as James Stewart, Antonio Cairoli and Australia’s own Chad Reed obviously having great input into the YZ range.

Despite weighing in heavier than the 2009 model, there’s no doubt that the new bike feels lighter and more precise in its handling, very much thanks to the increased mass centralisation.

With hard-pack sections, soft bulldust, mud, and more, the handling lived up to expectations at the Appin launch – especially when the power would shoot you to the next corner quicker than expected. Hey, I’m usually a 250F rider!

Feeling like I’d overshoot the turn for sure, I repeatedly found I could adjust my line quickly and turn it exactly where I had aimed, hitting one particular downhill left-hand rut lap-after-lap.

You point it in and shoot it out, and Yamaha even had a “Point and Shoot” EFI pre-set to match, which fit in well for the occasion. A mud map was also available, basically softening the entire powerband.

Wider turns are unreal as you power into them, hit your line, and then rely on the suspension to soak up the bumps on the exit while hard on the throttle.

Both the front and rear suspension suit the frame characteristics of the bike, feeling plush over the smaller bumps and riding them well, while still being stiff enough to tackle the harder bumps at speed and also working well on jump landings.

Even though it was an extremely hot day of testing at Appin with at least four hours logged on each bike, the suspension remained fresh and the heat didn’t affect the handling one bit throughout the day – even on the bikes that Jay and younger brother Ryan had thrashed moments before.

Speaking of the jumps, the manoeuvrability and stability of the bike in the air is confidence-inspiring in so many ways, typically enabling you to jump things quickly and be confident that you’re going to avoid trouble if you come up short or even over jump.

It’s only downfall in jumping is when you need to clamp hard with your legs, as my knee braces had a tendency to catch the plastics between the fuel tank and shrouds, most likely due to my shorter stature than the likes of Marmont.

As for the heat, some critics have suggested that the heat from the exhaust would cause concern on hot days around the legs, but this never proved a problem for me in my testing time.

Yamaha has come up with the goods in both handling and the engine departments, there’s no doubt about that. One thing that the bike does do quite often is wheelie, as you will notice in our video from the launch. I’m not sure if it’s a compliment to the engine or a downfall of the standard suspension, but it has a trait of wanting to mono when you’re hard on the gas on the exit of corners.

The brakes have a good feel but tended to feel a touch soft in the heat, lacking bite down the undulating high-speed hills at Appin, but that’s an easy fix with different fluid or brake pads should you feel the need.

At the end of the day, it’s a privilege to be invited to the Australian domestic launch of the new 2010 model YZ450F, and judging by the smiles on the faces of our local media, Yamaha has lived up to expectations with the new ride.

We’ve already watched James ‘Bubba’ Stewart win races on the bike in the United States on debut at the U.S. Open, but I have a sneaking suspicion we’re going to see the likes of Marmont and many local level riders winning races on the new YZ next season as well.

The new revolution in four-stroke motocross technology has arrived.

TECHNICAL INFORMATION:

CONCEPT
Yamaha’s all new 2010 YZ450F marks an all-new era for the manufacturer, and perhaps motorcycling all together. It’s revolutionary, out of the square, and completely unique for Yamaha in motocross machinery.

The standard approach to improving handing 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 featuring a 7.5-degree rearward-slanting engine with a straight intake tract mounted in a lightweight Bilateral Beam frame.

The YZ450F’s new-generation packaging exemplifies the synergy between engine and chassis. The frame allows use of a straight intake tract for improved intake efficiency, while the rearward-slanting cylinder contributes to mass centralisation.

Because the locations of the intake and exhaust are reversed, the locations of the airbox and fuel tank are also reversed. The more vertical fuel tank means the bike’s centre of gravity is lower and the bike is less influenced by changes in fuel volume.

The result, says Yamaha, is a less tiring riding experience and a bike that corners with less effort.

CHASSIS
A new Bilateral Beam aluminium frame sits at the heart of the YZ450F development project – a similar concept to the YZ250F frame but the execution is very different.

The 450F frame was developed using a new structural analysis method, consisting of sixteen components and made using a revolutionary new semi solid die-casting technology High Solid Die Casting, which allows complex shapes to be made stronger.

Thanks to this new-generation layout, both sides of the frame are more symmetrical, a characteristic which contributes significantly to overall chassis feeling, according to Yamaha.

For the right and left tank rails, aluminium shaped by the hydro-forming method is used. The materials used for the other parts include forged aluminium for the right and left arm tensioners and the upper half of the down-tubes, and extruded aluminium for the right and left halves of the lower parts of the down-tubes.

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 from 300 to 310mm. The valve damping specs have also been revised.

The offset of the triple clamp has been reduced from 25 to 22mm, while the caster, trail and other dimensions have been optimised in relation to each other to help achieve a high-level of handling performance.

The handlebar crown is made of cast aluminium and the under-bracket is made of forged aluminium. The same 2009 model four-step adjustable handlebar position features again. The axis of the handlebar bracket is offset and there are two attachment holes each for the handlebar holder, which makes for a choice of four different handlebar mounting positions – two on the bracket side and two on the crown side.

By moving the airbox 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, with the swingarm another symmetrical piece of the project.

The position of the rear shock has been moved 30mm lower, while the shock cylinder diameter has been increased from 46mm to 50mm for greater capacity. The stroke on the rear remains the same as on the existing model. The bump rubber has been optimised to improve the feeling when bottoming.

The damping valve has also been revised in the shock to enable riders to feel the damping effect from the start of the compression stroke.

The swingarm has been designed to match the positioning of the rear shock absorber along the central axis of the machine. The basic design of the irregular cross-section swingarm is the same top-bottom asymmetrical design as that on the 2009 model.

To help realise the chassis design concept of good longitudinal flexibility and high lateral and torsional rigidity, the swingarm has been produced by the hydro-forming method just like that on the existing model.

Furthermore, the thickness of the rear axle clamp has been increased for greater rigidity.

A new flat seat has been adopted, while the lightweight plastic resin fuel tank features a new design and is placed under the seat to contribute to the centralisation of machine mass and a lower centre of gravity.

Lightweight exterior parts have also been introduced, including a thinner front fender, rear fender, front number plate, front fork protector, side covers, air scoop, sprocket, a plastic resin engine guard and lightweight electrical parts.

ENGINE
Yamaha’s all-new YZ450F engine is an astonishing piece of machinery, a move that Yamaha considers as revolutionary as its first four-stroke motocross race bike, the YZ400F, when it was released in 1998.

The YZ450F development team have reversed the locations for intake and exhaust and create an all-new engine layout, which is done to ensure a straight intake tract for efficient cylinder filling.

The airbox is now located where the tank was, so the intake tract has 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.

By adding curves to the exhaust pipe between the exhaust port and the muffler, Yamaha has maintained an exhaust 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.

The 7.5-degree rearward-slanting cylinder with its downdraft intake offers other benefits in addition to improved intake efficiency, massively changing the handling effects of the bike despite it weighing more than the 2009 model.

According to Yamaha, one of the drawbacks of the four-stroke engine is its comparatively heavy cylinder-head, but by slanting the cylinder rearwards, the engine’s inertial mass is concentrated more towards the centre of the machine.

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.

The newly-designed liquid-cooled DOHC, single-cylinder four-valve engine is engineered to provide power development characteristics that make for better drivability for a 450cc motocrosser while also contributing to better centralisation of machine mass.

It features a compact four-valve combustion chamber with a bore and stroke of 97.0 x 60.8mm. The bore has been widened by 2mm and the stroke shortened by 2.6mm compared to the 2009 model.

For the compact combustion chamber, the two intake valves have a diameter of 36mm and the two exhaust valves have a diameter of 30mm and the valves’ pinch angle is reduced to 21.5 degrees.

This creates a compression ratio of 12.5:1 (compared to 12.3:1 on the ’09). Its shortened stroke reduces the height of the engine for better centralisation of machine mass, and the four-valve configuration enables the spark plug to be positioned in the centre of the combustion chamber.

The chamber itself is designed to create an effective air-fuel mixture tumble effect for better combustion performance that contributes to good response and power output. Also, the shapes of the ports have been optimised to provide better flow velocity.

The newly designed piston is a forged aluminium type and the cylinder is the same liner-less type as that of the 2009 model with ceramic composite plating. The intake/exhaust valves are also made of titanium like those of the 2009 model.

Offsetting the cylinder 12mm from the centre of the crankshaft reduces friction, and this is the first time on a Yamaha production bike that they’ve adopted an offset cylinder.

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.

Since 2006 Yamaha has used a dry sump with an oil tank in the crankcase, and for 2010 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 – increasing reliability.

A breather chamber has been added to the cylinder-head to assure effective separation of the oil and blow-by gas, effectively reducing oil consumption. Changes have been made in the camshaft cover breather chamber shape and passages to help contribute to a lower engine height.

The head cover and clutch cover are made up of a heat-resistant magnesium alloy, which has been used to reduce weight.

FUEL-INJECTION AND THE YZ POWER TUNER
Now featuring fuel-injection benefits include control over air/fuel mixtures in response to altitude and temperature changes. To go with it, Yamaha has developed an easy-to-use plug-in fuel-injection setting tool, the YZ Power Tuner, that’s available as an aftermarket item.

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. For the fuel delivery, a 12-hole injector is used and the spray of atomised fuel is directed at the opposite wall of the intake port at an optimum angle. This combines with the new port shapes to contribute to outstanding combustion efficiency.

The distance between the injector and the intake valve has also been optimised and the combined effect with the large size intake valve diameter and the shape of the combustion chamber causes a positive flow tumble effect within the combustion chamber that increases combustion speed.

To accommodate the adoption of fuel injection, a large-capacity ACM (Alternating Current Magneto) has been adopted and the need for a battery eliminated to further reduce weight.

The YZ Power Tuner has been developed as an option so riders can adjust the fuel-injection and ignition timing as they please. It’s a compact tool that’s powered by AA batteries, featuring a liquid crystal display and it’s small enough to fit in a pocket.

A setting function enables users to adjust nine different setting points for fuel-injection volume and ignition timing. Nine maps can be saved in the memory function on the tool. Setting changes can be made easily without using a computer, simply by connecting the YZ Power Tuner to the coupler on the bike.

A monitor function enables the user to monitor data from the various sensors, the engine running time and the malfunction self-diagnosis function for greater ease of maintenance.

The YZ Power Tuner is available from YMA as an aftermarket accessory.

Click here for our videos from the launch

Click here for the official Yamaha preview videos

Click here for more tech images and info