DKW RT 125

The RT 125 was a German two-stroke motorcycle made by DKW in Zschopau in the 1930s, IFA and MZ in the 1950s and early 1960s, and DKW in Ingolstadt in the 1950s and 1960s. "RT" stands for "Reichstyp" or "National Model".

In the 1930s DKW pioneered the Schnürle two-stroke loop scavenging process to dispense with the use of a deflector piston and improve efficiency of the combustion chamber. DKW also developed a highly efficient arrangement of transfer ports. These two features were included in the RT 125 to great commercial advantage. Competitor companies such as Adler and TWN copied the adoption of flat-topped pistons and strove to develop equally transfer port arrangements without infringing DKW's patent.

Copies of the RT 125 were built by at least eight different entities in at least six countries.

In 1938, after the German government discovered that RS Stokvis en Zonen, the Dutch importer of DKW motorcycles, had Jewish directors, they forced DKW to remove their franchise from the company. The RT 100, a smaller version of the RT 125, had been popular in the Netherlands, and RS Stokvis en Zonen commissioned Royal Enfield to make a motorcycle just like the RT 100. The resulting motorcycle, the Royal Enfield RE, copied the frame and front suspension of the RT 100, but its engine did not use Schnürle loop scavenging because Royal Enfield did not know about the system. The engine size was increased to 125 cc to improve the power output. Few were made before production stopped in October 1939, when Royal Enfield converted its factory to war production.

After a demonstration of the capability of the DKW RT 100, the War Department ordered a military version of the RE, designated the WD/RE, for use with airborne troops. This version, nicknamed the "Flying Flea" featured rigid forks and folding footrests and controls, including handlebars. Because Royal Enfield could not provide enough WD/REs to satisfy the demands of the military, the James Cycle Co was commissioned to build the ML, a Villiers-powered version of the Flying Flea. Royal Enfield and James both built civilian versions after the war.

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