TIMELINE
1965: CB450 K0 is the first ‘big’ bike from Honda and challenges the existing order with a dohc engine with torsion-bar valve springs and electric start.
1968: CB450 K1 gets a five-speed gearbox, restyled tank and new seat cover. The K0 model remains on sale throughout 1968, too. Claimed power for the K1 is now 45bhp at 9000rpm.
1969: CB450 K2 gets a new, painted tank without chrome panels and a redesigned seat.
1970: CB450 K3 features a 19in front wheel with a disc brake fitted, plus megaphone-style silencers and a larger tail light.
1971: There are minimal changes to the CB450 from 1971-on. Only different colour schemes and minor details differentiate K4-K7 models.
1972-1974 : CB450 K5, CB450 K6, CB450
1975: CB500T is introduced with a longer-stroke crank in its CB450 engine. Frame, bodywork and cycle parts are mostly new.