Gear Ratio
In a 4-stroke engine, the camshaft rotates once for every two crankshaft rotations.
This is determined by the working principle of a 4-stroke engine.
The crankshaft rotates twice for each cylinder to perform one power stroke, so one engine working cycle is two revolutions.
However, the valves only need to open and close once within one working cycle, so the camshaft rotates once per engine working cycle.

Transmission Methods Between the Crankshaft and Camshaft
There are three types: gear drive, chain drive, and toothed belt drive.
Gear drive offers high accuracy and reliability, but is noisier.
Chain drive offers low resistance and high reliability, but is also noisy and requires lubrication.
Toothed belt drive offers low noise and requires no lubrication, but has a slightly shorter lifespan, generally requiring replacement every 30,000 kilometers.