TheRT 125 was a Germantwo-strokemotorcycle made byDKW inZschopau in the 1930s,IFA andMZ in the 1950s and early 1960s, and DKW inIngolstadt in the 1950s and 1960s. "RT" stands forGerman:Reichstyp, English:Realm Type.
In the 1930s DKW pioneered theSchnürletwo-strokeloop scavenging process to dispense with the use of adeflector piston and improve efficiency of the combustion chamber. DKW also developed a highly efficient arrangement oftransfer 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 efficient transfer port arrangements without infringing DKW'spatent.
Copies of the RT 125 were built by at least eight different entities in at least six countries.
AfterWorld War II the Soviet Union took plans, tooling and even several dozenpersonnel aswar reparations toMMZ in Moscow (later transferred toMMVZ and SMZ) and to a factory inKovrov, and produced copies of the RT 125 as the M1A Moskva and K-125 respectively.WFM of Poland made a modified version of the RT 125 (underSHL 125 andSokół 125 brands), developed into 125/175 cc family motorcycles, produced until 1985.
RT 125 plans were also taken to the United Kingdom where they became the basis of theBSA Bantam, and to the USA where they formed the basis of theHarley-Davidson "Hummer" (Hummer is really just a few specific years, but generally people call the Harley lightweights Hummers).
After theSecond World War, DKW's factories in Zschopau were in theSoviet occupation zone. As such, they were under the control of the Soviet Union until they were handed over to the government ofEast Germany. The factory continued production of the RT 125 under the MZ (Motorradwerk Zschopau) brand into the 1950s.[1]
Meanwhile, DKW had reorganized itself inIngolstadt, where it began production of the RT 125W (for "West") in 1949. Variants of the RT 125W, usually with larger engines, were in production throughout the 1950s.[2]
In the 1950s, after reestablishing themselves as manufacturers of musical instruments,Nippon Gakki decided to use the manufacturing equipment left over from wartime production to make motorcycles. Since the copyright on the RT 125 had been voided by the Allies, the companyreverse engineered it as the basis for their first motorcycle. Nippon Gakki formed theYamaha Motor Company in 1955 to build their copy of the RT 125 as theYamaha YA-1, which was in production from 1955 to 1958. The YA-1 inherited design characteristics of RT 125 and, due to its thin body and chestnut brown tank, was affectionately nicknamed theAka-tombo (赤トンボ, "Red Dragonfly").[3][4][5]