CC / CI (Engine Displacement)

CC stands for cubic centimetres and CI for cubic inches. Both measure an engine's displacement: the total volume the pistons sweep as they move from bottom to top of their stroke, added up for all cylinders. One cubic inch is about 16.39 cc, so a 107 CI Harley-Davidson engine is roughly 1750 cc.

Displacement is calculated from bore and stroke. A larger engine usually produces more torque, but power also depends on design, revs and tuning, so a modern 700 cc twin can outperform an older 1000 cc engine.

In Europe displacement also matters for licensing: 50 cc mopeds are for AM licence holders, up to 125 cc (and 11 kW) for A1, and A2 is limited by power (35 kW) rather than engine size. Check your country's exact rules before buying.