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And what an engine it is!
The RG500 streebike exists because of 500GP racing. Pure and simple, it IS a streetgoing cousin of the world-championship-winning RG500s of the 1970s and 1980s. And the engine is the heart of the matter.
In 1963, Suzuki's Grand Prix team were proud to debut the new RZ63 racebike... featuring an incredible, water-cooled, square-4, disc valve, two-stroke engine... making 52 HP at 12,500 RPM and able to hit 140 mph.
This would turn out to be the oldest forefather of our beloved RG500.
The RZ63 was fast, but fragile. It developed into the RZ64, RZ65 (are you getting the pattern here) .. There was actually an RS67 in 1967, a V4, 125cc racebike! Suzuki lost the thread for a while, focusing on the XR11 (the racing relative to the GT750 engine), while they took a break from square-4 engines.
But in 1974... they came back to papa. Barry Sheene was hired to help develop the new bike and the XR14 (RG500) grand prix bike featured a 114hp, 54x54 disc-valve square-4, with a top speed of 175 mph and, amazingly, NO FRONT DOWNTUBES - in an attempt to make the bike as narrow as possible. The "open frame" led to some sketchy handling, but the bike showed glimpses of devastating speed, and ended 5th in the world championship, with no race wins.
1975 saw an updated RG500 end up 4th and 6th in the individual championship, and 3rd in the manufacturer's standings.
in 1976, the 290lb, 183 mph RG500 won the world title under Barry Sheene and took Suzuki to its first manufacturer's championship. In slightly updated form, the XR14 repeated the indivdual and manufacturer's titles in 1977.
For 1978, Susuki unleashed a shortened version of the square engine by stepping the crankshafts. This is the layout that we claim as our heritage.
Interestingly, all of these early RG engines were 54x54 bore and stroke, instead of the streetbike's 56x50.6.
Makoto Suzuki was one of the primary designers of our favorite stepped-crank engine. Here's a fantastic interview with him on the subject of developing the XR22 engine/ racebike.
https://www.pistonheads.com/news/ph2/makoto-big-mac-suzuki-ph2-meets/31837
Compact, powerful and straightforward, the square-4 disc valve is a hell of a powerplant.
Click image to enlarge
The RG500's Glorious Engine
