Jurgen van den Goorbergh on the Weber MUZ, with this bike he got 2 pole positions in the 500cc class.
Back in the good old days, different makes of 500cc bikes were powered by the mighty Swissauto V4 500cc engine with more than 200 hp, such as Weber MUZ, Aprilia, Pulse and Elf. This engine was also very succesfull in sidecar racing. Most of these bikes have an ROC frame.
For more pics see
Exotic 500cc V4 two strokes