A camshaft uses egg-shaped “cams” to open and close engine valves (one cam per valve), while a crankshaft converts “cranks” (the up/down motion of the pistons) to rotational motion. Located in the ...

Most inline-four engines use a flat-plane crank, meaning two pistons rise while two fall, giving perfect primary balance and even 180-degree firing intervals. Yamaha broke from this in 2009 with the ...