Drawing on the knowledge gleaned from building the CRF150 and 250, the 450's engine was comprehensively redesigned. The Unicam top end now features a four-lobe cam with individual rocker arms for each exhaust valve instead of forked rockers like before. That cam now spins directly in the cylinder head, instead of in a bolt-on cam mount. A 3.5mm-shorter connecting rod works with flywheels that are cut to clear the lightweight forged slipper piston, reducing engine height. A shallower combustion chamber, shorter titanium intake valves with narrower stems, redesigned valve springs, a pressed-on cam sprocket, narrower transmission gears and the use of four (instead of six) clutch springs further contribute to downsizing and weight savings. The rerouted exhaust also plays a part, exiting the cylinder on the left and wrapping around to the right, allowing the muffler to be positioned farther forward, closer to the center of mass. The net result of all these changes is an engine that revs to 11,450 rpm (up from 11,270), offering greater power over a broader range. Claimed output is 56.3 bhp and 37.5 lb.-ft. of torque.