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2007 YAMAHA MOTOCROSS – THE WINNER’S CHOICE Using the most advanced race-bred technology developed from our GP winning MX1 and MX2 race programmes, Yamaha’s engineers have further refined the winning YZ450F and YZ250F models for the new season. Both bikes feature a number of significant improvements to their engine and chassis designs which are aimed at further boosting engine performance and delivering even lighter handling qualities. Few, if any, other machines can come close to matching the YZF’s track record, and the new features and the advanced technology introduced for 2007 are aimed at reinforcing and extending Yamaha’s position as the leading manufacturer of race-winning motocross machinery. Our YZ 2-strokes are recognised as being amongst the very best in their respective classes, and both the YZ250 and YZ125 feature a number of chassis-focused upgrades for the 2007 season aimed at delivering even lighter handling and quicker turning performance. Famous for their instantaneous power delivery and ultra-light handling characteristics, the YZ250 and YZ125 are sure to be fighting it out at the front once again in the year ahead. 2007 YZ450F The most obvious change to Yamaha’s 2007 model YZ450F is stylish new white bodywork which will be available in addition to the original blue design. Equipped with white fenders, fuel tank, and sidepanels which complement the aluminium chassis, the new white model gives the YZ450F and fresh and radical new look. From a technical viewpoint the new 2007 YZ450F features a number of detail changes to the engine, as well as a significant range of critical changes to the lightweight aluminium chassis, all of which are aimed at refining this winning machine’s engine and chassis performance.
YZ450F ENGINE Revised balancer ratio for more powerful engine character The balancer shaft in any modern 4-stroke single performs two crucial roles. Firstly, it smoothens out the engine’s power delivery for improved rider comfort, and secondly, it allows the use of lightweight engine and chassis components which would otherwise need to be much sturdier in order to withstand vibration-induced fatigue. Rotating in the opposite direction to the crank, this balancer shaft makes life easier for the bike and its rider. For 2007 Yamaha’s engineers have revised the ratio between the balancer shaft and the crank for two reasons. Reducing the relative inertial force of the balancer shaft has improved the engine’s power characteristics and throttle response, and the reduced gyroscopic forces help to lighten the YZ450F’s turning characteristics. Optimum carburettor settings and revised exhaust valve lift A number of important changes have been made to complement the modifications to the balancer mechanism and to boost low to mid range power character. The carburettor settings are revised for 2007, and the exhaust valve lift has been modified to achieve optimum overlap – and to match these changes a new CDI unit is fitted. New titanium exhaust For 2007 a new titanium exhaust pipe replaces the stainless steel design used in 2006, and the diameters of both the exhaust and silencer are increased. These changes help to boost low to mid range power quality, and meet new noise regulations. High rigidity clutch pressure plates As well as transmitting power when compressed with the friction plates, the pressure plates on a clutch also plays an important role in helping to dissipate the heat generated. For improved durability and also to reduce the resistance at the clutch lever, the new YZ450F features new high rigidity pressure plates that reduce distortion, and in order to reduce the overall thickness of each plate, the number of clutch and friction plates increased. Reinforced radiators The large capacity radiators are now equipped with a reinforcement bracket for added strength, and the louvred panel design is modified for improved airflow. 2007 YZ450F Engine Technical Highlights 450cc 4-stroke liquid-cooled YZ450F CHASSIS New lightweight forged aluminium triple clamps Yamaha’s designers have made a large number of improvements to the YZ450F chassis for 2007, many of them aimed at further improving the lightness of the handling. Both the upper and lower triple clamps are new for 2007, and are now manufactured from forged aluminium, compared to the cast design used in 2006. Further weight savings are made by the fitment of shorter fork clamp bolts in the upper and lower triple clamps, and the handlebar mounts feature a smaller diameter M10 fastening bolt. Not only do the forged clamps and associated parts reduce overall weight, but their revised rigidity also helps contribute to the feeling of lighter steering that enhances overall ride quality. New wave type discs Any weight reduction is significant, but weight saved at an extremity of the machine – or from any part of the unsprung chassis – reaps the greatest rewards in terms of enhanced handling performance. The fitment of new wave type front and rear discs has a double benefit, as the discs are both part of the unsprung machine, and are also at the extremities of the motorcycle, well away from the bike’s centre of gravity. Featuring irregular shaped holes, the wave type discs not only reduce weight, they also enhance braking performance, and can also offer improved pad cleaning properties in muddy conditions. Further weight savings are made with the use of a newly designed brake hose. New front fork outer tubes The 48mm Kayaba front forks have also shed some weight for 2007, and now feature new outer tubes which are both lighter, and also offer a revised rigidity balance for improved handling qualities. Pro Taper handlebars New Pro Taper handlebars are used to achieve an improved riding position and give an enhanced appearance. The bulged section also features useful reference marks allowing the rider to experiment with different bar positions. New lightweight rear shock The innovative rear shock with its titanium spring has been lengthened by 1.5mm for 2007 to give a slightly higher ride height to achieve an even lighter handling feeling, and the use of new aluminium components in its construction reduces overall weight. Range of stainless coatings and lightweight parts The surface coating of many nuts and bolts is now stainless for improved appearance, and in order to minimise weight the following components have been modified: Fuel tank insert nuts Seat foam Rims Chain guard Chain slipper Rear frame Rear axle Axle end of swingarm In addition, more than fifty bolts have been made lighter
2007 YZ450F Chassis Technical Highlights New lightweight forged aluminium triple clamps Following a total redesign for the 2005 season and significant chassis updates for 2006, the YZ250 has once again proved to be one of the most desirable 250 2-strokes available. Featuring a state of the art aluminium chassis equipped with Yamaha’s innovative balanced rigidity technology, this high-tech motocrosser offers riders a winning combination of precision handling and high agility. And with its explosive 250cc long-stroke YPVS engine, this legendary quarter litre 2-stroke delivers an instant power and impressive torque. Changes for 2007 are aimed at refining what is already one of the most sophisticated packages available, and are concentrated around the lightweight chassis. Redesigned front forks The 48mm Kayaba front forks are recognised as being one of today’s leading designs, and for 2007 the outer tube walls have been modified. The change reduces weight, and the rigidity balance has been revised in order to give a lighter steering feel for improved handling performance. Pro Taper handlebars New Pro Taper handlebars are fitted as standard equipment for 2007, and the new aluminium bars not only reduce weight, but also offer a better riding position, with the grips positioned higher and further forward. New mounts are used in association with the new handlebars to accommodate the larger diameter clamped section. Redesigned lightweight rear shock The 2006 YZs were the first models to feature a lightweight titanium rear spring, and for 2007 Yamaha take the lightweight rear shock concept one stage further. A number of steel components in the shock are replaced by a range of new aluminium components, including the spring guide, lower mount and damping adjuster mechanisms. Ergonomic front brake lever For better feel and more efficient operation the 2007 front brake lever has been redesigned, and now features a flatter profile where the rider’s fingers make contact. Aluminium front wheel axle nut Any reduction in unsprung weight is desirable, however small, and the latest YZ250 features a new aluminium front axle nut in place of the steel item used previously. YZ250 Technical Highlights Liquid cooled, 250cc single cylinder 2-stroke with YPVS YZ250F The YZ250F made its mark when it totally dominated the 2005 MX2 World Championship, taking the first three places overall, while Yamaha took the 2005 MX2 Manufacturers’ Championship. And with the Yamaha YZ250F occupying five out of the top seven overall positions in the 2005 MX2 World Championship, this free revving 250cc 4-stroke is rightly regarded by many as the machine against which all other bikes in the class should be judged. With its combination of a rider-friendly power delivery, class-leading handling and lightweight steering, it is easy to see why the YZ250F has become one of the dominant bikes in the MX2 category. For 2007 Yamaha’s engineers have focused their resources on achieving enhanced high rpm performance, together with even lighter handling qualities and stronger front braking power. YZ250F ENGINE Optimisation of the intake, exhaust and ignition systems Although the basic architecture of this MXGP-winning 5-valve DOHC engine remains the same, a wide range of improvements to the intake, exhaust and ignition systems ensures even greater performance at high rpm and also in the over-rev range. These changes include a redesigned diffuser pipe, modified carburettor air vent passage, and new carburettor settings. Revised engine mounting angle The YZ250F is already renowned for its lightweight handling qualities, and to further enhance this reputation the 2007 model benefits from a revised engine mounting angle. In effect the engine has been rotated around the drive axis so that the cylinder is more upright. This change, together with the use of a range of new components including a lightweight engine guard ensures even lighter feeling handling. Magnesium crankcase cover Further weight savings are achieved with the use of a new magnesium crankcase cover which is 168g lighter than the previous design. Lightweight oil tank The dry sump engine features a separate oil tank positioned in front of the engine, and for 2007 a newly designed tank is fitted, featuring an additional internal partition which improves the oil/air separation. This has allowed our engineers to reduce the engine oil volume by 100cc, thereby saving weight. 2007 YZ250F Engine Technical Highlights 250cc 4-stroke liquid-cooled YZ250F CHASSIS Please note that the YZ250F benefits from all of the same chassis improvements described in the ‘YZ450F Chassis’ section, and also features a number of YZ250F-specific changes as follows. Repositioned head pipe In order to accommodate the more upright engine angle, the YZ250F’s frame has been modified, and the head pipe is now slightly closer to the rider. The frame’s rigidity balance has also been modified by the use of a smaller diameter engine mounting bolt, while the engine mounting plates are also redesigned to allow for the new engine mounting angle. The effect of these changes is to give a slightly more compact riding position, which makes for improved handling qualities, particularly when entering turns. New design front brake system One of the primary aims for 2007 was to reduce weight, and this has been achieved by the use of a new compact front brake caliper. By reducing the piston size and redesigning the master cylinder and brake lever, we have been able to reduce overall weight by 228g, while at the same time increasing braking performance. The YZ250F also features new wave type front and rear discs for 2007, and the discs fitted to the YZ250F are of a lighter design than those used on the larger YZ450F. New front fork axle bracket In addition to the use of new fork outer tubes (please refer to ‘YZ450F Chassis’ section), the YZ250F also benefits from new front axle brackets. The new axle brackets offer a better balance, and complement the new front brake caliper to give progressive and controllable braking performance. New shape engine guard The shape and mounting position of the engine guard have been modified, resulting in a 75g weight saving, and this contributes to the lighter feeling handling of the 2007 YZ250F. Revised radiator hose layout As well as the radiator changes outlined in the ‘YZ450F Chassis’ section., the YZ250F also benefits from a new hose layout which features lighter, more compact components while still offering the same coolant capacity. New rear shock link For 2007 the YZ250F is equipped with the same relay arm, bearings and spacer as fitted to the YZ250 2-stroke, resulting in both weight savings and optimised strength. 2007 YZ250F Chassis Technical Highlights The following changes are specific to the YZ250F Chassis: Repositioned head pipe New lightweight forged aluminium triple clamps YZ125 The YZ125 2-stroke enjoys a strong following amongst riders who have moved up from the 85cc class and who have chosen to stick with 2-stroke technology while they gain further race experience. And there’s also a hardcore of YZ125 fans of all ages who just love the fast and furious action that comes with 125 2-stroke racing! With its low overall weight and free revving 125cc engine, the YZ125 is a fierce competitor that is capable of running with bigger bikes, especially on tighter tracks where agility is more important than outright power. For 2007 this ever popular lightweight features the same chassis modifications as the latest YZ250. Please refer to the YZ250 copy for details.
YZ125 Technical Highlights Liquid cooled, 125cc single cylinder 2-stroke with YPVS YZ85 Available in standard or large wheel (LW) options, the YZ85 is the machine of choice for champions of the future. With all the style and technology of our larger YZ strokes, the YZ85 continues to set the standard. For 2007 the YZ85 features new graphics. YZ85 Technical Highlights Liquid cooled, 85cc single cylinder 2-stroke
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