The Yamaha YZF R6 is powered by an ultra-compact, DOHC, 16-valve, liquid-cooled, in-line four-cylinder with titanium valves. With a 67mm bore and 42.5mm stroke, this is one fast-revving power plant that features a red line set at an unbelievable 16,000 rpm. The Yamaha YZF R1, on the other hand, packs a larger 998cc version of the motor. The R1 is also the only production bike to feature a crossplane-style crankshaft, with an uneven firing order. The end result is an engine that produces the most linear torque possible. When coupled with the Japanese company's trademark YCC-T throttle system, riders enjoy instantaneous throttle response and increased engine control.