In an Enfield Bullet motorcycle, decompression refers to a mechanism that helps reduce the compression pressure in the engine cylinder during the starting process. It assists in overcoming the resistance caused by the high compression ratio of the engine, making it easier to kick-start the motorcycle.
The decompression mechanism typically consists of a lever or a button located on the handlebar or near the engine. When engaged, it lifts the exhaust valve slightly off its seat, allowing a small amount of the compressed air-fuel mixture to escape from the cylinder. This reduces the overall compression pressure in the cylinder and makes it easier for the kick starter to turn the engine over.
Once the engine starts running and gains momentum, the decompression mechanism disengages, allowing the exhaust valve to fully close and the compression pressure to build up normally for efficient combustion.
The decompression system is particularly useful in older Enfield Bullet models, which often have a higher compression ratio and require a stronger kick to start. Newer models may incorporate electric starters, eliminating the need for manual decompression during starting.