The Honda CB450 was the first 'big' Honda motorcycle with a 444cc 180° straight twin, dual overhead cam engine producing 43-45 horsepower (more than 100 HP/ liter).
Appearing first in the 1965 four-speed K0 model, and progressing through a series of 'K' models with various improvements and styling changes, notably a redesigned fuel tank and 5 speed transmission in the 1968 K1 model. In Canada the K1 model was marketed as the Hellcat.
The CB450 was first shown in UK during the Diamond Jubilee Brighton Speed Trials of September 1965, traditionally held along the seafront. As the bike was newly imported, the engine was not run-in, so the appearance was a semi-competition demonstration sprint run for publicity ridden by (the late) Allan Robinson, MBE, a Honda staff member, recording a standing-start kilometre time of 30.1 seconds and a terminal speed of 100 mph (160 km/h).