The idea of a Grand Prix bike built for road use is a perennial favourite, but although there have been many race-styled bikes over the years only a few bare much resemblance to real championship winners. However, Suzuki’s RG500 was the real deal and remarkably similar to the successful Suzuki RG500 GP racers.

The initial RG500 GP bike was launched in 1974 and went on to win four 500cc World Championships, two (1976 and 1977) in the hands of Barry Sheene. Italians Marco Lucchinelli and Franco Uncini took the titles in 1981 and 1982. It was also extremely successful in the hands of privateers and one of its most memorable victories was at Laverton in 1976 when Kenny Blake on an customer RG500 beat reigning 500cc World Champion Giacomo Agostini on the factory MV Agusta.

Suzuki RG500 Gamma

As two-strokes totally dominated Grand Prix and F750 racing in the late 1970s and early 1980s, there was a considerable resurgence of interest in production performance two-strokes. Most were 250s and 350s, and when Yamaha released their RD500C four-cylinder Suzuki countered with a production version of the RG500 square-four that was by now pensioned off in Grand Prix racing (Suzuki took a three-year hiatus in 500 GP from 1983).

The production RG500 was released at the Cologne Show towards the end of 1984 with the first RG500G appearing in April 1985. It remained almost unchanged until the 1987 Model Year and total RG500 Gamma production was only 9284, plus 6213 400cc RG400s for the Japanese market.

Suzuki RG500 Gamma

The Gamma retained the race bike’s water-cooled square-four layout with four carbs and rotary valves. This complex engine featured two transversely mounted crankshafts geared together. As on the final racing units the rear crank was mounted slightly higher than the front. Diagonally opposed cylinders fired simultaneously, cancelling vibration and obviating the need for complex balance shafts.

Suzuki’s AEC (Automatic Exhaust Control) system was modelled on the Yamaha YPVS, delivering a smooth torque curve without sacrificing top-end power. Transmission was also closely based on the racer, the six-speed cassette-type gear cluster accessible from the side of the engine without dismantling the crankcases. The bore and stroke were 56×50.6mm, and with four Mikuni VM28SS flat slide carbs the power was initially 95 horsepower. Production versions were detuned to 77 horsepower at 9,500 rpm.

Suzuki RG500 Gamma

The chassis was mid-1980s state-of-the-art: a box-section alloy beam aluminium frame, full-floater rear suspension, and an air-assisted 38mm front fork. The fork also included a four-way adjustable Posi-Damp anti-dive system. The wheels also echoed contemporary design practice; a wide 17-inch rear mated to a 16-inch front. The brakes were awe-inspiring for 1985, with dual four opposed piston calipers on the front gripping 210mm slotted discs. These were more than enough to haul down the 154kg RG500.

Riding the RG500 back in the 1980s was an eye-opening experience. Light and powerful, the bike was a real flyer. The engine pulled cleanly from 3,500rpm, hitting 160 km/h when the 8,000rpm power band kicked in. In top gear the Gamma was a genuine 230+ km/h motorcycle with razor sharp handling to match.

Suzuki RG500 Gamma

The light weight combined with a short 1425mm wheelbase, 25-degree steering head angle and 16-inch front wheel ensured the RG500 went where it was pointed. And there was something uniquely intoxicating about the feel of the four-cylinder two-stroke engine. My friend Ray thrashed his RG500 back in the mid-1980s, leaving us all in a two-stroke haze. But we caught up with him when he had to replenish the fuel tank, 22 litres of leaded petrol disappearing alarmingly quickly when the RG500 was ridden hard.

With their high emissions of particulate matter (lubricating oil) and unburnt hydrocarbons (about 30% of fuel comes out of the exhaust unburnt) the day of the high performance two-stroke was numbered. Ultimately environmental legislation spelled the Gamma’s demise but they were always an acquired taste.

Buyers eschewed the Gamma in favour of the new generation of high performance four-stroke such as Suzuki’s own GSX-R and unsold stock remained available for several years after production finished. Now, perfect standard Gammas are extremely rare and sought after, and it is one of the most collectable motorcycles of the 1980s.

Suzuki RG500 Gamma

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Steve Wood
Steve Wood
2 months ago

Hi Ian,
interesting read thanks. I owned and raced 2 different RG500 GP bikes, a MkII from 1979 – bought from Dave McCulloch (Suzuki dealer in WA), and an RGB500 (Mk5) in mid 80’s – ex Glen Middlemiss. I had some reasonable success on them both, but more so on my TZ500H I’m between.

A bit of background detail:

Not sure about the road version, but the GP bikes were 4 individual cranks, not 2. Other differences were the Mikunis we’re 35mm and had steel rotary disks on the GP bike and plastic I believe on the road bike (wee used to have a lot of the disk centres crack and would chew out the disk covers pretty badly, always had spares on hand.

The MkII was a bit of a pig to handle, we had to build a subframe under the swing arm to stiffen it as she used to wallow really badly under hard power coming out of corners.

Lots more info about the GP engines if you want to know.

I look forward to reading more of your articles.