Valve Control (four-stroke)
In a side-valve engine, the valves are operated from the "underhead" cam without special valve gear. OHV engines have valves operated by pushrods. OHC and DOHC engines have overhead camshafts typically operated by chain, belt, gear train or bevel gear drive.
Honda equipped the CBR400F with REV (described as "revolution responding type valve pausing mechanism") in 1983, This system enabled to switch over the number of valve operations per cylinder between low and medium speed revolution range and high speed revolution range. In 2002, Honda introduced HYPER VTEC in the VFR800 Interceptor. In 2006, Kawasaki introduced VVT in the Concours 14.
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