Words: Ollie S. Images: Yamaha Motor Corp.
For the good part of a year rumours surrounding Yamaha’s plans to introduce an all new 4-stroke revolution were rife within the industry and all the industry reliant businesses accumulated in the urban stratosphere. Instant dismal contracts were issued by Yamaha Global worldwide and tongues were effectively clipped insuring that absolutely nothing leaked. What followed from such a mammoth global control effort from Yamaha was an expectation factor that grew widely out of proportion. Within the last few months leading up the release of the highly anticipated twenty-ten YZ250F there were leaked photos on the internet of some Greek technicians CRT monitor showing the possible blue prints of what we now refer to as gospel. That poor character was made redundant (or so the rumour is told) and then Yamaha released information on the brand new YZ250F which stunned the world followed by dropping the next bombshell “where the bloody hell is the 450”.
Fast forward a month and news of the YZ450F has spread like a global disease or moreover a perfectly simulated and implemented PR campaign that surely must reap the dividends. Yamahas YZ450F for 2010 is so radically enhanced its a staggering thought that Yamaha had the ability to revolutionise the 4-stroke off-road world when it was an odds on bet that another manufacturer would beat them to the fold.
Like the new 2010 YZ250F the 2010 YZ450F has left no stone unturned in its quest to become the most technically advanced model overhaul to create a truly ground breaking machine. Of course the technology within its engine is nothing new to engine developers the globe over but it is however new thinking and intuitive development in the search for ultimate off-road performance. Yamaha took their time in implementing a fuel injected (FI) motocross bike into their quiver of machines sticking to their laurels that it had to be done right the first time or not at all. In the scheme of things the introduction of FI into the 2010 YZ450F is merely a sweetener to the total package; what lies hidden amongst the inventory of forward thinking changes is the generation leaping enhancements to the frame, engine, chassis, ergonomics and suspension.
YZ450F MAIN FEATURES
The new bilateral frame sits at the heart of the YZ450F development project and is similar the bilateral frame used in the YZ250F but having a very different execution. The new bilateral frame was developed using a new structural analysis method and the frame itself consists of 16 components made from four different aluminium processes using revolutionary semi solid die-casting which allows complex shapes to be constructed stronger with just the right amount of controlled flex. Thanks to the new technology the frame is more symmetrical allowing for a better overall feel and the frames ability to absorb and withstand forces and impacts with better balance and more consistent feel.
To accommodate the new frame the rear suspension has been positioned in line with the machines central axis. Its position has been made possible by the adoption of the frontal intake FI system. The position of the rear shock has also been moved around 30mm lower. Changes to the rear KYB shock absorber include an increased cylinder diameter from 46mm to 50mm for greater capacity whilst the stroke remains the same. The whole shock revision has created a damping force with new levels of rider control and feel.
In tune with the new frame and shock mount is a brand new swingarm that provides even greater linear cornering performance than 2009. The thickness of the rear axle clamp has been increased for greater rigidity whilst realising the total chassis design concept of good longitudinal flexibility and high lateral and torsional rigidity.
Whilst the rear shock is modified and aligned with the new frame Yamaha has also introduced brand new KYB speed sensitive front forks in order to improve shock absorption and smooth operation when entering turns at high speed. The damping valve specs have been recalibrated and the forks gain an extra 10mm of travel.
In conjunction with the upgrade to the frame and the speed sensitive forks the front fork triple clamps have had their offset reduced from 25mm to 22mm. The caster, trail and other dimensions have also been optimised in relation to each other to help achieve a high-level of handling performance. The triple clamps themselves feature the same four-way adjustability of new YZ250F handlebar mount clamp.
An all new seat has been introduced to take advantage of the new design aspects incorporated with the front intake and FI system. Additionally it takes advantage of the under seat fuel tank designed to centralise machine mass and lower the centre of gravity (COG).
In a back to the future attitude the YZ450F’s exterior bodywork adopts newly designed lightweight front and rear fenders, front number plate, front fork protectors, side covers and air scoop. The new body styling is sculptured with elements from the new fast and edgy looking arrow design aspect of the new YZ250F. Other lightweight advantages are the inclusions of the new-design sprocket and plastic resin engine guard and lightweight electrical parts as well as the magnesium cylinder, clutch, ACG and oil filter covers.
ENGINE
The all-new liquid-cooled DOHC 4-stroke single-cylinder 4-valve engine is designed and engineered to provide power development that makes for better driveability whilst contributing to a better centralisation of mass. Bore and stroke is now 97.0 x 60.8mm whilst the bore has been widened by 2mm and the stroke shortened by 2.6mm compared to the 2009 model. Compression ratio has been increased from 12.5:1 compared to 12.3:1 on the 2009 YZ450F.
The shortened stroke reduces the height of the engine for better mass centralisation with the new four valve head configuration making best performance from a centrally positioned spark plug. A unique new fuel injected engine with straight intake and a rearward-slanting cylinder has been realised by employing a combination of the latest FI technologies. The new layout totally challenges the accepted concepts of chassis design and introduced a new dimension not possible in a chassis developed for carburettor fed engines.
The advantages made possible with the new FI system are near limitless in the new YZ450F. To monitor changes in running conditions the FI system is updated constantly with information gathering equipped intake pressure, intake air temperature, current air pressure, crankshaft rpm, throttle position, and coolant temperature sensors. Based on data fed from those sensors the compact ECU calculates the optimum induction fuel volume. The fuel is feed through the 44mm Keihin throttle body from the front of the engine through a specific motocross developed 12-hole injector to spray atomised fuel at the opposite wall of the intake port. With the inclusion of FI, Yamaha incorporated a large capacity alternating current magneto to eliminate the need for a battery and further reducing overall weight. Unlike other cumbersome systems Yamaha’s FI system is completely tuneable by the user from an optional YZ Power Tuner setting tool accessory.
The YZ Power Tuner is a compact handheld unit that quickly plugs into the FI system port. It’s a robust tool that makes trackside tweaks a breeze with absolutely no need for a laptop as it features its own liquid crystal display and hard drive function.
Accompanying the rearward-slanting engine with frontal intake is a rear-positioned exhaust. It’s been dubbed the ‘tornado’ because of its curved shape and by the addition of the curves between the exhaust port and the muffler it maintains a similar length to the previous 09’ version whilst achieving a better centralisation of machine mass without sacrificing power output. A resonator chamber is also standard fitment inside the exhaust to ensure sufficient silencing whilst enhancing torque characteristics from the bottom to mid rev range.
With the arrival of the technologically advanced rearward-slanting engine Yamaha engineers took the concept to a new level by offsetting the cylinder 12mm from the crankshaft. The result is a massive reduction in friction due to the more efficient use of the force created by having the connecting rod vertical at the moment of greatest combustion force.
REBIRTH OF A LEGEND
Like the YZ250F the new YZ450F will be available in New Zealand in both Yamaha Blue and Special Edition White. Reading between the lines availability of the YZ450F probably won’t hit our shores till the thick end of December which leaves its availability for nationals 2009 lingering till the New Year.
Both the blue and white versions of the NZ YZ450F will come spec’d with the same black rimmed wheels as the YZ250F and have the same Pro Taper handlebars although the bodywork differs ever so slightly due to the under seat mounted fuel tank and front mounted intake. The optional YZ Power Tuner, as mentioned earlier, will not only contain the ability to personally fine tune the FI settings but has the ability to save new maps which can be stored on the tool and even shared to a friend’s YZ450F. In a similar fashion the YZ Power Tuner serves as complete diagnostic aid recording accumulated engine hours and logging any malfunctions as well serving as a real-time information monitor during any time of your ride. Currently there is no price on the YZ Power Tool and we don’t expect it to be cheap. However despite its features surely indicating a specialised cost the YZ Power Tool will serve as an integral part of owning a YZ450F for the future.
Yamaha have certainly covered the entire spectrum in creating a truly spectacular machine. If the machine is going to be anything as good as it is on paper in the dirt then Yamaha certainly have engineered a master piece; which was unquestionably the case with their recently released YZ250F. With a launch on the horizon for the all new YZ450F look out for a feature in the November issue of Kiwi Rider Magazine.
Click to open full specs below:
Click to view introductory video from Yamaha America: