What is the compression ratio of a motorcycle?

[VonMalia]

Currently, the vast majority of small and medium-displacement motorcycles (below 250cc) have a compression ratio of 10:1, with a few at 10.5:1. Therefore, both 90 and 93 octane fuels can be used. However, based on experience, higher octane fuels tend to provide better power performance. The differences between high and low compression ratios are explained as follows: Explanation 1: If a high compression ratio engine uses low-octane fuel, it may cause knocking. Knocking occurs when the air-fuel mixture ignites prematurely before the spark plug fires, while the piston has not yet reached the top dead center. This premature explosion is harmful to the engine. Explanation 2: Using high-octane fuel in a low compression ratio engine can lead to the spark plug firing before the air-fuel mixture is compressed to an optimal ignition point. This results in incomplete combustion, which can cause carbon buildup and reduced engine power.