Suzuki RG50
GP replica
The original RG500 racer, which went into limited production in 1975 and was raced by Australian Jack Findlay the year before, is one of the most iconic and important competition motorcycles of all time. Not so much for its string of world championships in the 500cc class, which were achieved by works or works-supported machines, but for the fact that the square four was produced in sufficient numbers to ensure full grids in a class – despite being the so called ‘premier’ category – that was in danger of extinction, having degenerated into a re-run of the 350cc event. Now privateers could arm themselves with a highly competitive and reliable machine and go racing with a reasonable chance of success, which went a long way to putting bread on the table for the impecunious journeymen who roamed Europe.
But while the RG500, in its various successive models that culminated in the Mark 12 of 1987 was God-sent for the race riders, it didn’t do much for the road rider. That is, not until 1984, when Suzuki unleashed the production RG500 Gamma race replica on an unsuspecting public. Well, maybe unsuspecting might be stretching the truth, because Yamaha had stolen a march by releasing their own 500cc race replica, the RZ500, earlier in the same year, and speculation was rife that Suzuki would follow suit. Notice of intent was served by Suzuki in March 1983, when the RG250 Gamma made its public bow – a 250 twin with plenty of race cred and said by Suzuki to be the first in a new ‘Gamma’ family. The terminology, gamma being the third letter of the Greek alphabet, and presumably in this case representing the third development in a series, is a bit hard to understand, so maybe it just sounded right.
Then, late in 1984, at the IFMA Show in Cologne, there it was, perched high on the Suzuki stand – the road-going RG500 Gamma. Just what was inside the fairing at Cologne was not revealed, but clearly on display was the aluminium box-sectioned frame and Full-Floater rear suspension, along with an anti-dive front end carrying the then-fashionable 16 inch wheel. Naturally, the new RG500 was touted as being a close replica of the machines that had brought World titles to Barry Sheene, Marco Lucchinelli and Franco Uncini, but this was somewhat removed from the truth. However the basic concept was true to the racer – a square-four water-cooled 500 with rotary disc-valve induction, poking out a very healthy 75kW at the crankshaft and tipping the scales at just 154kg.
It was, as they are fond of saying in political circles, “a courageous move”, given that two strokes were increasingly on the nose and impending legislation would remorselessly drive further nails into the coffin of the ring-dings. The model, as both RG500 and the Japanese market RG400, lasted just three production seasons, from 1985 to 1987. The RG400, catalogued as the RG400EW, was identical save for the bore, giving a capacity of 397cc, with a 59hp output. Total production of the 500 was around 9,200, with a further 6,200 400s built in the three years. Like the racer, the Gamma was effectively two 250 twins doubled up (or more accurately, four 125 singles) with the crankshafts geared together, with a cassette-style quick-change six speed gearbox. This component was a boon to would-be racers, with the gearbox internals, including the shifting mechanism and the kickstarter easily removed by simply taking off the clutch and its backing cover. Connecting the cranks was a central shaft driving the water pump, ignition and alternator on the left side and the
wet clutch via a helical gear on the right. While the main frame was aluminium box section, both the steering head and the central swinging arm pivot sections were in cast aluminium, welded to the frame sections. All of this was coated with a process called Duralite to prevent corrosion. The rectangular section swinging arm itself was also aluminium, with a single central rear shock absorber; the system, pioneered on the successful motocrossers, used the Suzuki name of Full Floater, with a vertical shock absorber behind the gearbox, and carried a 17-inch rear wheel. The carrier for the caliper sat above the disc, while the torque arm was below, running back to the frame. Up front were 38mm forks which carried one of the many forms of anti-dive that virtually all manufacturers were experimenting with at the time. Suzuki called theirs Posi Damp, and like its competitors, it was probably more successful as a marketing tool than in any practical sense. It was actually a means of progressively increasing the compression damping, a system that had already been tried on the heavyweight GSX1100 EFE, with a choice of four settings. The idea of restricting the tendency of the front end to dive under braking was laudable, but it also had the effect of creating a hydraulic lock in extreme conditions, a situation which produced an almost rigid front end just when you didn’t need it most. The fork legs themselves carried air-adjustable pre loading. Twin-piston callipers acting on a pair of drilled discs did the actual stopping. Not surprisingly, Suzuki had its own acronym for the front brake system – DPBS – or Deca Piston Brake System (the company seemed to have a serious addiction to Greek words at the time, Deca meaning ‘ten’). This system actually used ten small pistons, a total of four in the two front calipers, and two in the rear unit – 4 + 2 = 10. Like Yamaha’s YPVS, (and later Honda’s ATAC – Auto Torque Amplification Chamber), the RG500 employed what Suzuki called SAEC (Suzuki Automatic Exhaust Control) – acronyms were the flavour of the month in Japan at the time. Using a rotating barrel to raise or lower the exhaust port height, this effectively increased or lowered the volume of gas reaching the exhaust pipe expansion chamber, and was controlled by the engine’s Capacitor Discharge Ignition unit. All these systems had the same intent and result – to broaden the power band by allowing larger exhaust port openings at high rpm, while reducing the effective size in the low and mid-range. In the RG’s case it meant a usable power range from 5,000 to 10,000 rpm. The front pair of expansion chamber exhaust pipes swept around the engine and under the crankcase in normal fashion, while the rear pair came straight out the back of the reversed cylinders and exited on each side of the seat. The engine itself mirrored the later model race RG’s “stepped” layout with the front pair of cylinders lower than the rear. As well as exposing the rear cylinders to the airstream, this allowed the gearbox to be brought forward, shortening the engine’s front-to-rear dimensions. The road machine used the bore and stroke from the original Mk1 RG500 – 56mm x 50.6mm – which wasn’t a stepped design, but later came to be using dimensions of 54mm x 54mm. The rectangular slide-type carburettors sat on each side of the crankcase with air ducted from filters mounted under the seat. Nice racer-style trimmings like alloy clip-on handlebars, a recessed fuel filler in the 22 litre tank and an excellent super slim fairing copied directly from the track machine added to the package. There were of course practical differences between road and racer, such as iron cylinder sleeves in the seven-port barrels instead of Nikasil, but the production roadster when released produced only 4hp less than the original ‚
The RG400, catalogued as the RG400EW, was identical save for the bore, giving a capacity of 397cc, with a 59hp output.
RG500 (XR-14) racer, despite the addition of mufflers and a comprehensive air filter system. Two stroke technology, although under threat from the legislators, was now divided between the schools of reed-valve controlled piston port induction, and the much rarer rotary disc valve crankcase induction. In the case of the latter, there were really only two players when it came to mass production; Suzuki, and Kawasaki with their tandem-twin KR250. Excessive crankcase width was one bugbear, plus the extra expense of the precision machining required. In the Gamma’s case, the front and rear cylinders fire 180 degrees apart, so the positive pressure in one crankcase helped to draw the mixture into the other as the pistons rose. Naturally, Suzuki’s target was the Yamaha RZ500, and in many respects, the RG was superior, at least in principle. It was lighter – by 26kg in dry form – more compact and slimmer, but after the clamour created in Cologne in November 1984, the Australian buying public had to wait almost one year for the arrival of the real thing. A major hurdle of course, was making the new Suzuki comply with the Australian Design Rules and European standards, and this took time. And by the stage that the RG reached our shores in the second half of 1985, it was up against some serious competition in the sporty road bike stakes, not just from the RZ500 but the stunning new FZ750, Yamaha’s five-valve rocket which would blow the wheels off bikes of far greater capacity and horsepower.
Still, there were those who simply hankered for a real Grand Prix replica, and were prepared to stump up a fair wad of dosh – $5399 when released in Australia – to own one.
Climbing aboard
Although I’ve ridden a few racing RG500s, which varied in specification quite a bit from the Mk1 of 1975 to the final Mk12, I’d never had the opportunity to try a road version until Dick Lipscombe offered me a ride on his. It’s a remarkably clean machine that has had very little done to it since Dick purchased it a few years back from Old Gold Motorcycles at Londonderry in Sydney’s north west. And while I have always found the racing RG500s cramped, with a high seating position and low-set handlebars that initially gives you the impression that you’ll be launched over the front under severe braking, the road bike, let’s just call it the Gamma, is entirely different. The seating position is low and comfortable; quite an achievement given that the fat exhaust pipes are routed under the seat.
No electric starter here, but the right-side kickstarter is a cinch to operate – just a steady prod is enough to bring the engine to life, but like the racers, it needs a decent reading on the temperature gauge before the bike will run cleanly or idle. While this was happening there’s a chance to take stock. The instruments consist of speedo, tacho and a combined fuel and temperature gauge – perhaps the most important of the lot. The rest of the accoutrements such as switches and levers are pretty much standard Suzuki fare of the time. Now for some fun. Despite the fairly limited confines of the ‘test track’, the Suzuki is a delight to ride. There’s plenty of flexibility in the engine and virtually none of the old-world peakiness associated with two strokes. It feels like it would rev well past the 10,000 rpm red line, but there’s no point as power begins to drop off after 9,500. It’s the beefy mid-range power that’s most impressive, no doubt a product of the Suzuki ‘power valve’ system. And there are more gears in the 6-speed box that I need on this occasion in the interests of licence preservation.
I really wished this were a race track instead of a suburban back street, because the RG just wants to go, and tipping into corners becomes an enjoyable exercise in weight shifting and throttle control. The brakes are adequate without being startling, but brakes like to be used regularly and this bike had not seen a lot of action for a while. I think the front stoppers would have improved with a day’s riding, but they were still perfectly up to the task at hand. All too soon it was time to hand back the RG to its owner. Damn! This is the sort of motorcycle on which you could play all day. It’s easy to see why the RG500 Gamma has become such a cult machine around the world, with numerous owners’ groups and chat forums. There are worthwhile tips on tuning and maintenance, including how to push the stock 95 hp by around 40%. Now that would be worth trying.