From Kevin Cameron at CycleWorld
The R3’s engine is a parallel twin of 68.0 x 44.1mm bore and stroke, the bore exceeding the stroke by the same high 1.55 oversquare ratio as in the 2015 R1. Yamaha learned the value of having a signature sound from the crossplane-crank R1’s “V-8 voice,” and in giving R3 a 180-degree crank will achieve a syncopated, interesting sound. This is a liquid-cooled sport engine, with DOHC, four valves per cylinder, fuel injection, and forged pistons.
Peak power comes at 10,750 rpm and will likely be in the vicinity of 45 hp. Its “offset cylinders” lessen friction by reduc*ing the angularity of the connecting rods on the power stroke, thereby pressing the pistons less hard against their cylinder walls. The liner-less bore is not hard-plated as in the Nikasil process but instead relies on the hardness of myriad silicon particles already present throughout the part, honed smooth and then treated. This saves 3 to 4 pounds in liner weight and adapts well to production.