The RG Γ 500 won two consecutive Riders' Championships in the 500 cc class with Marco Lucchinelli in 1981 and Franco Uncini in 1982.

Like its GP forebears, the road-going RG was powered by a 498 cc naturally aspirated, rotary-valve inducted, twin crank square four two-stroke engine.

This was a popular feature on early 1980s sports bikes and was supposed to control the tendency of a motorcycle's nose to dive under braking.

However, the main differences between the two were a reduced bore width (50mm instead of 56mm) with power output reduced to 59 bhp (44 kW), different big end roller bearings (some roller-less), clutch disks unit, front brakes (non floating discs), silencers, and 'RG400' stickers on the fairings.

The RG400 was produced and sold within Asian markets: its 397cc capacity and 59 bhp (44 kW) output complied with a restricted Japanese motorcycle driving licence of the time.