Complex sentence: The original R65 was made up until 1984 with a smaller frame than larger R series motorcycles, but in 1985 the R65's engine was put into the new (and larger) R80 frame which featured a single rear shock absorber (mono-shock).
Split into simpler sentences: The original R65, with a smaller frame than larger R series motorcycles, was manufactured until 1984. In 1985 the R65's engine was put into the new (and larger) R80 frame which featured a single rear shock absorber (mono-shock).