In the seventies and eighties two stroke multi-cylinders were common in sidecar track racing. In Germany they used König and homemade Yamaha triples as first made by Rudi Kurth. Later Suzuki GT750 and Yamaha TZ500 and 750 were used. in 1980 multi-cylinders were banned.
Found some great pics of a very rare RG500 powered sidecar racer. This is actually the first RG500 sidecar that I have seen. It was raced in the GP's in 1979. The chassis was made by Klaus Sprengel of alloy plates he bought from Louis Christen (LCR). The RG500 is a works engine with Bartol cylinders. For more pics see Suzuki RG500 sidecar racer