1. FKS by Franz Krause Fahrzeugbau, Berlin S14, 1921-1925
These machines had 148 cc engines which were attached above the front wheel which it drove via belt. The engines were probably supplied by Kirchheim of Magdeburg.
2. Fritz Kläger Spezial FKS, Freiburg, 1966-1970
Built racing motorcycles of 250cc to 500cc.
Kläger began racing in the early 1930s, achieving his first victory as an Ice Racer in 1934. After the war he became quite famous as both a rider and builder. He rode with the Horex GP team in the mid-1950s and appeared often on the podium. He took second in the German championship of 1957. After 35 years of competition he retired, in 1969. He died at the age of 93, in 2007.
Sources: GTU Oldtimerservice, wikipedia DE.