OHC Velocette

The OHC Velocette KTT motor, developed from the racers and introduced in 1929, was the first production racer. The camshaft is driven with two bevel gear setups and a vertical shaft with two Oldham couplings, not much changed from earlier OHC engines. 

1924 Prototype OHC Model K

The 1925 Model K was the first production machine.

The KN- Normal- was the designation for the 1929 and 1930 model. It would have featured the foot operated gear shift introduced in 1927.