A BMX bike with an engine
So a bunch of product planners and engineers got together at Yamaha's factory in Iwata and discussed their visions and ideas. Mitsuo Kitada, a manager of Yamaha engineering was one of them. He liked the idea of crossing a trial bike with a mountain bike. "Actually a trial bike is not so far off. However trial bikes have become real specialist machines for competition only. Unlike a decade ago, where you could still see them occasionally on the road, today you can only see them on trailers in the hands of competition riders."
Takeshi Higuchi adds: "Our main target was, to create a bike that was not difficult to ride and with only a bit of experience one should be able to perform standing still, little jumping or controllable wheelies. All these tricks should be carried out safely and at low speed, so they are easy to control. And on top of that, the bike was supposed to still be used as a mean of transport in particular in urban environment."
High-tech approach
Mitsuo Kitada decided to go for a high-tech approach in order to achieve the goal. He designed a lightweight aluminium frame, which is bolted very tightly around the engine. To sustain jumps and other tricks, the suspension would have to be sturdy. The first choice were motocross based parts. Front fork and rear suspension are derived from Yamaha standard YZ 85 motocrosser. The parts did undergo some modification regarding stroke and set-up. YZ 85 wheelbase proofed suitable and wheels too.
223 cc engine
"Of course a high performance motocross engine was totally out of question", Kitada continues. "We needed a four stroke with enough torque to do the job. The well known 223 cc powerplant from Serow, a lightweight offroad machine was chosen. This little engine is very pleasant to ride and has a fine pick up on throttle even at lower rpm", Kitada explains his choice.