The 650 was the last of SOHC4s, with production beginning in 1979, while the others ended production in 1978. The 650 engine is essentially a factory bored and stroked 550 engine, in a redesigned frame. There were several other changes made with the 650, primarily with the electrical systems. Many of these changes were also used on the DOHC4 bikes that Honda began producing in 1979.