As regards engine performance, we decided on a maximum output of 8500rpm, placing the usual emphasis on high-rpm output characteristics while seriously considering the low-to-mid rpm range that will be most frequently used by the entry user.
In keeping with the engine's characteristics, and in order to maximize the effectiveness of air intake volumes in all ranges up to 8500rpm, we debated the optimum size of valves and pistons and the best number and positioning of cylinders. In the end, we opted for a liquid-cooled parallel twin-cylinder engine with a bore/stroke ratio of 67mm×66.8mm.
At the same time as keeping vibration to a minimum by using pins phased at 180°on the crankshaft and a couple balancer behind the cylinders, we also achieved an engine that looks compact and stylish.
The crank counterweight specifically shaped for couple balance, not only enabled us to obtain the crankshaft moment of inertia required to achieve the characteristics of an easy-to-handle engine, but also meant it was possible to make it thoroughly lightweight.
Flow analysis of the cooling liquid through CAE simulation maximized efficiency in cooling performance, which enabled us to make the water pump smaller and more lightweight, but still more than capable of doing its job during periods of high output.
In order to maximize air intake and exhaust efficiency, we straightened the profile from the air cleaner through the intake port to the exhaust pipe. Although the diameter of the valves was increased, along with that of the intake and the exhaust, the valve stems were made narrower, reducing friction and increasing exhaust efficiency.
Furthermore, in order to achieve easy-to-handle characteristics in the low-to mid-rpm range and sustained pull at high revs, we exhaustively analyzed air intake and exhaust mechanisms to calculate the ideal length and diameter of pipe required.
Intake and Exhaust Port