Yamaha har nå avduket sin nye YZ450F, som så langt er det eneste nytt for neste år fra den Japanske produsenten.

YZ450F ble på forhånd omtalt som en ”verdensnyhet” som ville skape stor interesse i bransjen. Den største nyheten med sykkelen er at sylinderen er lagt bakover istedenfor fremover.

Hvorvidt den nye YZ450F er en verdensnyhet og vekker den store begeistringen blant kunder og bransjen for øvrig, skal vi la andre bedømme. Her er videoene av YZ450F.

Foruten YZ450F er også de fleste andre 2010-modeller nå sluppet i USA uten særlige oppgraderinger, og det kan se ut som Yamaha tar seg en god pust i bakken når det kommer til oppgraderinger for 2010.

Farger:
YZ450F kommer i to farger:
2010_YZ450F_01_1252503701_250x187.jpg2010_YZ450F_02_1252503776_250x187.jpg

YZ450F Presseinformasjon på engelsk:

The 2010 YZ450F – a machine made for corners
Every motocross rider wants a machine with exquisite handling – it lets you zip through corners, get on the gas sooner on the other side, and makes the bike less tiring to ride. So for 2010 the YZ450F has been completely re-designed with one goal in mind handling better than anything else on the track.
Yamaha has always understood that races are won and lost through the corners, and that only supreme handling allows a bike to effortlessly fly through the turns. The 2010 YZ450F has a unique, fuel injection, rearward-slanting engine in a revolutionary Bilateral Beam aluminium frame. Every element of these has been designed to ensure a synergy between engine and chassis that makes the bike corner better than ever before.

Replacing carburettors with fuel injection allowed the designers to completely redesign the YZ450F, repositioning the fuel tank and air filter and developing the revolutionary rearward-slanting engine. Having the cylinder inclined backwards allows a straight intake design, giving greater intake efficiency and more power. Combined with the new frame, the new engine also lowers the bikes centre of gravity and helps to centralise the mass of the machine. Better mass centralisation improves ease of use and means a rider can turn with more confidence and agility, zipping past opponents and shaving precious seconds off lap times. The rear shock and spring revision ensures this power comes with a high traction feel through the turns. It all combines for race-winning corners and super-responsive handling.

TECHNICAL HIGHLIGHTS

Engine
-New 450cc, liquid-cooled, 4-stroke, 4-valve rearward-slanting engine, which brings improved intake efficiency and better mass centralisation
-Fuel injection
-Excellent mass centralisation from new layout
-Compression ratio improved from 12.3:1 to 12.5:1
-Magnesium used to lower weight of cylinder head cover, clutch cover and oil filter cover
-Widened bore and shortened stroke for more power
-YZ Power Tuner accessory for tweaking fuel-air ratios in the field

Chassis and styling
-New aluminium Bilateral Beam frame for perfect rigidity balance
-Ergonomic frame designed to be easier on riders muscles
-Weight reduced with lighter fuel tank, fenders and side covers
-New design centres mass for better cornering
-Aggressive new styling

TECHNOLOGIES EXPLAINED:

ENGINE

For 2010 the YZ450F has a revolutionary new fuel injection, liquid-cooled, 4-stroke, 4-valve, DOHC, single cylinder engine. Its new layout optimises power, intake efficiency and mass centralisation.

Revolutionary rearward-slanting engine
Conventional wisdom has it that cylinders should be forward-canted, with fuel delivery from the rear and exhaust from the front. But a straight intake delivers a more efficient cylinder filling, and at Yamaha we like to innovate. The YZ450F engineers swapped the fuel intake and exhaust to create a revolutionary new engine layout, with the cylinder slanted backwards. They created a layout that allowed a straight intake, but it also allowed them to concentrate the engines mass more to the centre of the machine, making it incredibly stable in and out of corners, and giving the bike a much lighter and more responsive feel.

Fuel injection
For the first time, the YZ450F comes with fuel injection, which automatically adjusts to give the best possible combustion under changing conditions. A throttle position sensor (TPS) and sensors for the intake pressure, intake air temperature, atmospheric air pressure, crankshaft rpm and coolant temperature constantly monitor how the engine is running and make adjustments accordingly. A compact, light, motocross-specific fuel pump has been used, made primarily of plastic resins and with a simplified layout for extra weight reduction. Fuel injection also gives greater freedom of engine layout for the fuel tank and intake/exhaust systems, allowing us to better centralise the machines mass.

To get the most from the fuel injection system, riders can use the YZ Power Tuner accessory to set the power development characteristics they need. It could be a richer fuel-air ratio in the lower rpm range to get stronger traction through mud, or perhaps a leaner mixture in the high-speed range so it revs lightly. The YZ Power Tuner is easy to use, has a simple interface, and doesnt require a cumbersome laptop. Adjustments can be made in the field, with easy-to-read and easy-to-set 3D program maps, so riders can make changes for the weather, changing track conditions, or their own feel for the course.

See ACCESSORIES, below, for more detailed information about the YZ Power Tuner.

Shortened stroke
To comply with the straight intake design, the YZ450Fs fifth valve was removed, giving the bike a more compact 4-valve engine, and a combustion chamber with a bore that has been widened by 2 mm to 97 mm and a stroke that has been shortened by 2.6 mm to 60.8 mm. The two intake valves have a diameter of 36 mm and the two exhaust valves have a diameter of 30 mm, reducing the pinch angle to 21.5 degrees. This all combines to further help mass centralisation. The compression ratio has been improved from 12.3:1 to 12.5:1, for even better power development.

Rear exhaust
The rear exhaust passes under the seat, and curves have been added to the exhaust pipe to maintain a length similar to the existing model while gaining better centralisation of machine mass. A resonator has been fitted to ensure sufficient silencing while also bringing out plenty of torque across a wide rpm range.

Front straight intake
The front straight intake brings excellent intake efficiency and helps mass centralisation. Because the intake ducts are in front of the engine, the engines heat has less effect on the intake air temperature and there is less chance of dust stirred up by wheels getting in to the intake system. It also allows the rear shock to be mounted closer to the machines central axis, further improving mass centralisation.

Offset cylinder
By offsetting the cylinder from the centre of the crankshaft we have reduced friction loss. Normally, when combustion forces the piston down, there is also a lateral force that pushes the piston toward the cylinder wall, causing friction. By offsetting the piston, friction loss can be decreased. This offset cylinder makes more efficient use of the force created by combustion, and is the first time such a cylinder has been used on a Yamaha production off-road competition model.

Lower and lighter
The camshaft covers breather chamber shape and passages have been changed to help lower the engine height. For the head cover and clutch cover a heat-resistant magnesium alloy has been used to reduce weight further.

CHASSIS

Bilateral Beam aluminium frame
The core of the 2010 YZ450F is the new Bilateral Beam aluminium frame. Different types of aluminium are used on different parts of the frame, according to the balance of strength and rigidity required for optimum performance. Because it has been formed so precisely, the frame has superb rigidity. As a result, sideways shock is smoothly converted into longitudinal, or up-down shock that is absorbed by the suspension. For the rider, this means a light, strong frame that handles wonderfully and can be moved in and out of corners with ease.

Long-stroke suspension
Supporting this revolutionary frame is a new suspension system. Both front and rear suspension units have more capacity, and the front fork has a 10 mm longer stroke.
This new fork is tuned for high traction under a variety of riding conditions and offers great damping precision. Even more remarkable is the forks supple operation when entering a corner, further enhancing the riders ability to overtake.

The new look
The gruff elegance of the YZ450Fs mechanics has been emphasised by keeping the body as bare as possible. The Bilateral Beam aluminium frame, rearward-slanting engine with straight intake tract, and mass-centralised engine are allowed to stand out, with as few plastic body parts as possible. Those that exist are aggressively styled a fishtail rear fender gives the impression of a departing motorcycle, and the riders view of the front fender has a shape to suggest lunging forward. Seen anywhere in the garage or roaring to the finish line this is a great-looking motorcycle.

ACCESSORIES

In fuel injection systems, data about engine temperature, air temperature, pressure and other factors is monitored in real time to ensure the best possible combustion in changing conditions. Information is fed from a throttle position sensor, and sensors that measure intake air temperature, coolant temperature, air pressure, intake pressure and crankshaft revolutions. This is supported by two 3-D program maps – a fuel injection volume map, and an ignition advance (ignition timing) map. Both include engine rpm and throttle opening as parameters. The standard maps, which the YZ450F leaves the factory with, are tuned to bring out the best performance in a wide range of conditions.

In race conditions, however, the smallest advantage can make a difference. The optional simple, hand-held YZ Power Tuner allows riders to alter the standard maps according to track conditions, weather and their own riding preferences.
Each map has three adjustable points, one each for low-speed, mid-speed and high-speed. There are also three points for throttle opening, giving nine adjustable points in total.

On the fuel injection volume map, adjustments can be made over a range of 15 steps, from -7 to +7. This means the fuel injection volumes can be reduced or increased by up to 21%. The volume of fuel is controlled by lengthening or shortening the injection time, so this map is often called the injection timing map.

Adjustments for the ignition advance map are made over a range of 14 steps, from -9 to +4 at each of the nine points.

The two maps combine to become a customized FI setting map. Riders can then set a number of different maps for different riding conditions.

Other accessories include:
-Radiator guards
-Frame guards
-Skid plate
-Sticker kit with seat skin