| Topic | Summary |
| Crankshaft |
The crankshaft rotates in the main bearings in the crankcase. Connecting rods are attached to offset areas called throws where the reciprocating motion of the piston is changed into rotary motion. |
| Engine bearings |
Bearings support and protect rotating parts and let them turn freely. Bearings can be either plain, usually called bushes, slippers or shells, or they can be anti-friction with rolling balls or rollers. |
| Flywheel |
The flywheel is mounted on the rear of the crankshaft. It links the crankshaft to the transmission, through the clutch. With manual transmission, the flywheel is very heavy, and its momentum helps smooth out engine operation. |
| Reciprocating action |
Reciprocating means going back and forth over the same path. Reciprocating action is used to make rotary action and has many applications. |
| Crankshaft & bearings |
The crankshaft turns because of the forces transmitted through the connecting rods. It is held in place by bearings. |
| Valve train overview | In the 4-stroke gasoline engine, the inlet and exhaust ports are opened and closed by valves. These valves need a system to control how they work. |