MZ BK 350 Two Stroke Flat Twin

The MZ BK 350 (short for "boxer kardan 350 cc") was produced from 1952 to 1959, by Motorrad Werk Zschopau in East Germany. The BK 350 was the first new design to come out of the former DKW factory after World War 2, and was initially offered under the IFA (Industrieverbad Fahrzeugbau) brand.

Contrary to the popular claims, the two cylinder oppossed piston two stroke engine isn't a Nazi-era aircraft donkey engine (jet starter), even though DKW had designed a 250 cc boxer donkey engine that never reached production.

The BK engine was developed alongside another IFA project, the much better known and more traditional AWO 452 four stroke single.
Two stroke boxer motorcycles such as the BK 350 are very rare, a similar layout was used by Villiers in the 1930s but otherwise boxer engines are much more likely to be found in four stroke motorcycles like the legendary BMW airheads.

Several thousand machines were produced, but the BK never reached the popularity of the smaller MZ singles or the AWO; and from 1956 onwards the BK was replaced by the MZ ES 250, first in the long successful line of 250 cc singles produced in Zschopau.

Image from Deutsches Zweirad- und NSU-Museum