Yamaha's 2015 YZF-R1 was introduced to the global motorcycle market not so long ago by none other than Valentino Rossi. The 2015 Yamaha YZF-R1 weighing under 200kg fully-loaded, making 197 horsepower and loaded with a full array of MotoGP style electronics, the new Yamaha YZF-R1 is a completely new machine and shares extremely little with its predecessor beyond its name and the crossplane crank philosophy.
Yamaha are also upfront about its intended use, Hideki Fujiwara, Yamaha YZF-R1 Project Leader, told the press “The main aim was simply to build the fastest motorcycle on the track. Instead of thinking how to improve the old YZF-R1, we asked ourselves where we wanted to be, looked at the goal, and developed from there. So we effectively started from scratch/”
The 2015 Yamaha YZF-R1 engine is lighter and more compact, with new bore and stroke, compression ratio, barrels, cylinder head, cases, crank, rods, pistons, valve-gear, fuel injection and airbox. Basically, everything is new. The crank – still with four crossplane-oriented crankpins at 90º and a 270º – 180º – 90º – 180º firing interval – is lighter, with 20% less rotating inertia for quicker engine response. It still needs balancing to counter a strong rocking couple, but the balance weight are now lighter. Titanium rods are fracture-split and 40% lighter than before, while new-shaped, forged aluminum pistons are lighter and stronger, with new, coated rings and a newly-designed oil-jet cooling system. At the top end, redesigned valve-gear includes finger rockers instead of bucket and shim, to reduce weight and thus permit greater valve control at high rpm.
The shorter stroke and wider bores mean a lower average piston speed, which allows the rev limit to be increased by 1000rpm. The airbox capacity is 23% larger than before, to provide more fresh air for the engine. This air is channeled through variable-height intake funnels. The fuel injection has been revised with a new spray pattern to improve combustion efficiency, and the 4-2-1 exhaust is almost entirely made from titanium. The result is a claimed 197 horsepower at 13,500rpm, and peak torque of 112.4 Nm at 11,600rpm.
When asked how close the new Yamaha YZF-R1 engine is to the layout in the MotoGP Yamaha M1 motorcycle, Fujiwara said “It's difficult to put this into a number, but I would say the new Yamaha YZF-R1 engine, in design terms, is something like 80% similar to the Yamaha MotoGP M1 engine. But we have also made a very big jump with the electronics with the 2015 Yamaha YZF-R1, and I can say that if the engine is 80%, the electronics are more than 90% similar to the Yamaha MotoGP motorcycle.”