Yamaha two-wheel drive motorcycle

Sunday November 16, 2003 In one of the most significant moves in motorcycle history, Yamaha has announced that it will release a two-wheel drive motorcycle early in 2004.Though it is not the first two-wheel drive motorcycle in history, the new machine will be a landmark model as it seems certain to be the first of many - testing over the last five years has indicated enormous benefits in terms of safety, traction and (probably the one that counts most) outright cornering speed in slippery, sandy or muddy conditions.

Though the first motorcycle to be offered with Yamaha's 2-Trac system will be an off-road competition machine based on the WR450F enduro machine, tests on an R1 1000cc supersport road bike have shown an incredible speed differential on wet tarmac - tests at the tight Swedish Karlskoga roadracing circuit showed the 2-trac-fitted R1 to offer a whopping five second per lap advantage over a standard machine when the circuit was wet.

The motorcycle looks set to begin the next phase of its 100 year development with the release of the first production two-wheel drive machine.Developed by Yamaha in conjunction with the race department of 'hlins (best known for its competition shock absorbers), the release of the new machine is the culmination of nearly twenty years of testing of both mechanical and hydraulic two-wheel-drive systems. Research initially began in secret in 1985 but then in 1998, a prototype 2-trac-equipped YZ250 motocross bike was revealed to the press, and the following year, Yamaha-raced a 2-trac-equipped TT600R in the UAE Desert Challenge.

In 2001, Jean-Claude Olivier, President of Yamaha France, raced a 2-trac-equipped WR426F into fifth place in the rally of Shamrock. Then, in 2002, David Fr'tign' and Olivier scored a 1-2 finish for the French TEAM at the shamrock rally aboard 2-trac-equipped WR426Fs.

How it works

The patented 2-Trac system uses a hydraulic pump located above the gear box, and driven by a chain (in an oil bath) driven from the gear box.

The system comprises a pump connected by flexible hoses to a hydraulic engine located in the hub of the front wheel. The 2-trac is a closed loop system equipped with filtration system and is a self-regulated compact unit. The hydraulic pressure transmitted to the front wheel is proportional to the speed of the rear wheel: the more the rear wheel loses traction, the more the hydraulic system compensates by increasing the traction power to the front wheel. The distribution of the power between the front and rear wheels is variable in order to optimize traction. The front wheel can never turn quicker than the rear wheel, and the power transmitted to the front wheel is never higher than that used for the rear. This self-regulated system also allows for the conditions, so that the power to the front wheel is slowly reduced so that the rear wheel "recovers" traction.

When the throttle is closed, no power is transmitted to the front wheel, but if the throttle is opened abruptly and that the rear wheel starts to lose grip, the sudden increase in pump revs increases the hydraulic pressure of the system and a higher proportion of engine power is transmitted to the front wheel. If the rear wheel continues to spin, more power is sent to the front wheel. The proportion of the engine power provided to the front wheel is hence controlled by both the throttle and the traction of the rear wheel.

Mechanical or Hydraulic

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