Ahh, two-stroke engines. Many people associate the sound (and smell) of a two-stroke with backyard equipment, but for motorcycle fans it means something else entirely – performance. You see, before emissions regulations were as stringent as they are today, two-stroke motorcycles not only dominated off-road, but also the road and, more importantly, the racetrack. But how did it happen?
The two-stroke’s success story is one that involves Nazi missiles, treachery, industrial espionage and more intrigue than you can shake a bottle of castor oil, and it’s beautifully presented. in this 20 minute film by YouTuber Bart.
The first two-stroke engine was created in Scotland in 1881, but it wasn’t until 1908 that it became practical for use in motorcycles and scooters. These engines were used because they were simple and cheap to produce, but there was a noticeable ceiling on their performance, which caused most performance and racing motorcycle manufacturers to use four-stroke engines. .
This changed when a German rocket scientist, Walter Kaaden (the video claims he worked on the V1 missile, but that’s not true. He worked on the remote-controlled Hs 293 anti-shipping missile which was responsible sinking dozens of Allied ships along the way) started tinkering with a DKW 125cc motorcycle after the war. He eventually took that bike race which caught the eye of the IFA racing team (which DKW was absorbed into post-war), who hired him to lead their racing efforts.
Kaaden’s greatest contribution to two-stroke engine design has been the perfection of the exhaust expansion chamber, which would allow the engine to breathe more efficiently and which would increase the power by about 20% compared to engines with normal exhaust pipes. The technology is still used today with modern two-stroke engines.
Eventually, Kaaden was brought to work for East German motorcycle manufacturer MZ, where he continued to innovate and increase two-stroke power outputs. In 1961 Kaaden’s MZ 125cc racing engine became the first naturally aspirated engine to produce 200 horsepower per liter of displacement (that’s 25hp for you non-mathletes out there), a figure that is still incredibly impressive today.
Of course, nothing gold can stay, and eventually MZ’s top rider Ernst Degner signed a secret deal at the Isle of Man TT with then-struggling bike maker Suzuki to give them the technology. de Kaaden in exchange for 10,000 GBP (equivalent to about $183,143.57 in today’s money) and a full factory tour for the 1962 season. Degner defected from the East German Republic and the MZ motorcycles at the Swedish Grand Prix in 1961. He escaped in the trunk of a car.
Two-stroke bikes remained the dominant force in grand prix motorcycle racing until 2002. After that, the rules were restructured around a 990cc four-stroke engine design. It’s rare now to hear the classic “ring-a-ding-ding” exhaust note of a two-stroke motorcycle anywhere but on the dirt because of emissions, and even those are becoming less common. Still, they were important, and damn it, they’re pretty cool.