 A smaller 397 cc derivative, known as the RG400, was also developed and produced alongside the 500.This machine appeared identical to its bigger brother in every way, making use of the same frame, suspension, and gearbox.However, the main differences between the two were a reduced bore width (50mm instead of 56mm) with power output reduced to , different big end roller bearings (some roller-less), clutch disks unit, front brakes (non floating discs), silencers, and 'RG400' stickers on the fairings.