In 2006 the RS50 was restyled and was given a new engine.
The RS50 was given the D50B0/B1 50cc 2-stroke liquid-cooled engine produced by Derbi. D50B1 engines can be identified by the engine number containing the D50B0 or D50B1 mark. In 2010 the RS50 was further restyled and give the name RS4 50. The RS4 still features the same 50cc 2-stroke liquid cooled engine produced by Derbi.