A crankshaft is a rotating shaft that converts reciprocating motion into torque. Crankshafts are used in internal combustion engines, where they convert the linear piston motion into a rotational motion that drives the engine’s output shaft.
The crankshaft is stroked by the up-and-down motion of the pistons. The crank throw is the distance between the centerlines of the main bearings, and it’s what determines the stroke of the engine - how far up and down each piston goes. The connecting rods connect each piston to the throws on opposite sides of the crankshaft.
The strokes of a four-stroke engine are intake, compression, power, and exhaust. The intake stroke sucks air and fuel into each cylinder through an open valve at the top of each cylinder (the intake valve). During compression, both valves are closed and the piston moves up towards the head, compressing air/fuel mixture. This process can be thought of as squeezing because work is done on air molecules to decrease their volume (and increase their pressure). When ignition occurs during power stroke(firing order 1-3-4-2), gasoline vaporizes and expands in volume rapidly due to heat from spark plugs igniting it inside cylinders (this increases pressure which forces pistons down). After combustion takes place during power stroke ,exhaust valve opens as piston moves back up and pushes out burned gases (exhaust) from previous cycle .