Distribution
Motorcycle valve timing refers to the synchronization of engine valve movements with piston movements, controlled by the camshaft. Timing plays a crucial role in the engine's smooth operation, ensuring fresh air intake and exhaust gas evacuation at the right times. Here's a description of the main components involved in motorcycle timing:
Camshaft: The camshaft is a rotating component located in the engine block. It comprises cams, lobes or bosses that determine when the valves open and close. The camshaft is usually driven by the timing chain or timing belt, and is positioned to control valve opening and closing.
Valves : Valves are moving components that regulate the flow of air and fuel into the combustion chamber, and allow exhaust gases to escape. There are generally two types of valve: intake valves and exhaust valves.
Valve springs: Valve springs ensure the rapid, controlled closing of valves after they have been opened by the camshaft. They also hold the valves in place as the pressure in the combustion chamber increases.
Tappets (if fitted): Some engines use tappets to transmit the movement of the camshaft to the valves. These tappets can be hydraulic to automatically compensate for backlash.
Timing chain or belt: transmits camshaft movement from the crankshaft. Timing chains are generally more durable, while timing belts are quieter.
The timing cycle consists of four stages: intake, compression, combustion and exhaust. The camshaft synchronizes the opening and closing of the valves to match these beats of the engine cycle.
There are also different types of timing system, such as single overhead camshaft (SOHC), double overhead camshaft (DOHC), and more advanced configurations like the desmodromic system used by Ducati. These systems aim to optimize engine performance by controlling throttle distribution more precisely.
