The primary factors for cam selection are engine displacement, mechanical compression ratio, and the most important: rpm range. However, other factors such as induction and exhaust airflow, stroke, rod length, rod-to-stroke ratio, gearing and total bike weight also come into play. Once these factors are known, camshafts with appropriate variables can be selected. Common camshaft variables include valve lift, duration, overlap, and the timing of the valve events (points at which the valves open and close). In the case of racing camshafts, rate of lift is also a factor. Nevertheless, these variables are critical in determining not only an engine's maximum power output but also the shape of its power curve.
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