Complex sentence: The Robin was first manufactured in October 1973, a direct replacement for the Reliant Regal, these models featured a 750cc but in 1975 the car gained a number of improvements including a engine boost to 850cc.
Split into simpler sentences: The Robin was first manufactured in October 1973 as a direct replacement for the Reliant Regal. These models featured a 750cc engine, but in 1975, the car gained a number of improvements including a engine boost to 850cc.