After WWII, BMW’s return to racing started slowly. In 1951 their first effort, called the Mustang, was a basic rework of their 1938 racing motor without the supercharger. They were not competitive. By late 1953 BMW brought out the 500 CC Rennsport (Racing Sport), a bevel gear driven dual overhead cam high compression racing motor that was very fast.
Walter Zeller was the only factory rider to have consistent success on the RS54 winning the German championship in 1954 and ‘55 while finishing 7th and 2nd in the world championships. The RS54 had some stability problems that kept the world class motor from reaching the pinnacle in individual racing.
It was when privateers bolted a sidecar to the RS54 that the real star was born. The third wheel eliminated the instability and the RS54 motor was fast. BMW would race the same design in the sidecar ranks into the 1970s winning 20 manufacturers championships along the way.
In 1954 there were 24 RS54 motors built. 4 of the 24 were pure factory bikes that had a shorter stroke and bigger bore than the 20 that were sold to privateers. The works bikes used a 5 speed transmission while the others were 4 speeds. Suspension was Earles front and dual shock rear with shaft drive. Weight was 286 LBS. BMW also offered a direct fuel injection option and several teams used the FI on long courses and carbs on the shorter tracks.
I would be incredibly careful buying this bike. The listing has limited information and the front forks and carbs are definitely not the stock items. The motor may well be a RS54, but I would want some certification. I think perhaps there is a reason why this bike is available at about half market price.
This particular 1954 BMW Rennsport RS54 (VIN# 004) is in Ojai, California and is listed as used. They do state that it has Ceriani front forks and a remanufactured frame. The bike is listed with a Buy It Now price of $90,000