Suzuki RG500 (1985-1989): Review & Buying Guide

Suzuki’s RG500 Gamma is the most authentic mass production 500 GP replica. Launched in 1985 and sold in the UK as part of Suzuki’s model line-up until 1989, the RG is now a much sought after sports bike offering a unique and never bettered multicylinder two-stroke experience.

Yamaha’s RD500LC (RZV500R in Japan) went on sale a year earlier, in 1984, but is heavier, less potent, and not as true to its GP inspiration as the Suzuki. Honda’s NS400R, launched the same year as the RG, isn’t in the same league as the Gamma either. Although sweet handling and beautifully engineered, the NS is actually a big 250 rather than a replica of Honda’s racing 500.

In fine fettle – jetted to maximise performance and lightly blueprinted – and RG500 can get within a whisker of 150mph on almost 100bhp. Although many big four-strokes produce more power, the RG’s light weight (around 160kg juiced) and screaming two-stroke powerband make it a uniquely exciting ride, even now. More importantly, the likes of the RG – large road-going strokers – will never make it into production again, so if you want to experience the thrill, Suzuki’s RG500 is still the only answer. Sporty four-strokes, like Suzuki’s own GSX-R750, were getting really good by the time the RG appeared, so development on two-stroke multis ground to a halt after the Gamma, making them – the best of the breed – into cult bikes overnight.

Owning an RG comes at a price, however. Values are high, salty even, as is the model’s appetite for unleaded fuel. Ridden hard, an RG500 can drink its way through its 4.8-gallon tank at a rate of under 20mpg… A tidy RG will set you back the fat end of £20,000-plus now, but values are still rising – slowly – so you shouldn’t lose out if you come to sell again. If you can afford one, riding and owning an RG500 is still a unique thrill. Buy one now before they’re banned for good…

Pros & Cons

Suzuki RG500 (1985-1989) – Prices

The RG500 was part of Suzuki’s UK range for four years, but in that time its technical specification changed little. Minor modifications, to aid reliability, were made in the bike’s first year – beefed up second and sixth gear ratios being one – but the RG’s overall spec went unchanged throughout its run.

Small spec changes between markets are more obvious. UK bikes came with rectangular front indicators on stalks. Other markets – Japan, for example, have their front winkers integrated into the front of the fairing. Imports also feature kph clocks. But differences are minor.

Because all models are fundamentally the same, G through to CH, values depend more on condition and originality more than year of registration. Genuine factory sanctioned race replica paint jobs (Skoal Bandit and Pepsi) are rare and can command a premium to some buyers.

 1985 RG500G

Original Suzuki 500GP for the road. Aluminium perimeter frame, 16/18in wheels, 95bhp, 154kg. Japanese black/red Walter Wolf replica features different clocks with WW logos. A 400cc version also sold in Japan with optional bellypan, 60bhp, and different bore and stroke. Colours: blue/white, red/white, Walter Wolf (Japan)

 1986 RG500CH

Mechanically and visually identical to G model. Skoal Bandit race colours a limited edition option for the UK market. Colours: blue/white, Skoal Bandit (limited edition, UK)

 1987-1989 RG500CH (E34)

Updated graphics and colours only. Pepsi replica offered for 1989. Some bikes still kicking about in showrooms as late as 1991. Colours: two-tone blue/white, red/white/black, Pepsi (1989)

RG500 values: Rough £10,000-£13,000; Tidy £15,000-£19,000; Mint £20,000-£25,000

Suzuki RG500 (1985-1989) – Engine & Performance

The Gamma’s compact engine is a square-four two-stroke, just like its GP racer inspiration, but with twin-ring pistons and a wet clutch for greater reliability. Running a bore and stroke of 56 x 50.6mm, giving 498cc, the cylinders fire two at a time (diagonally) with the twin crankshafts turning in opposing directions to minimise primary vibration.

The cylinders run Suzuki’s Automatic Exhaust Control (AEC) system – separate chambers just forward of the exhaust ports that fill with exhaust gases at low rpm, extending the tuned length of the exhausts to increase torque. At high rpm these chambers are closed by a servo motor, allowing gases a straighter, shorter exit out of the cylinders, aiding top end.

Mixture induction is direct into the crankcase via disc valves, just like the RG500 racers, fed by four 28mm Mikuni flatslide carbs. Suzuki claimed 95bhp @ 9500rpm for the RG which, like both the NS400 and RD500LC, was a tad on the optimistic side. A real world figure of 80-85bhp at the rear wheel is nearer the mark. Early press bikes were fettled by Suzuki (exhaust welds were cleaned up, jetting was optimised) so claims of 150mph and vicious powerbands filled period test reports.

A dry weight of just 145 kilos helps the RG’s cause, but once juiced (the tank holds 22 litres) the bike’s true weight is nearer 160kg. Despite that and the performance hyperbole from Suzuki, RGs are still exciting to ride. The engine’s more flexible than its GP heritage might suggest, but there’s a rush from 7000rpm right through to 10,000rpm that gives the Gamma more bite than any other 500GP replica. Fuel consumption can be an issue, however. Heavy use of the throttle can see average mpg tumble from a fairly respectable low 30s to a wallet bashing sub 20s mpg…

Suzuki RG500 (1985-1989) – Handling & Suspension (inc. Weight)

Just like the late model RG racers and RG250, the 500 Gamma chassis is a box-section aluminium perimeter design. Light, stiff and strong. Suzuki labelled it their ‘Multi-Rib Aluminium Boxsection Tubing Frame’, a step up from the previous RG250W chassis in that each box-section strut is further strengthened by the addition of ribbing on its edges. Suzuki claimed the design gave the frame increased rigidity for no extra weight, while the alloy used to create the RG’s chassis was a mix of aluminium, magnesium and zinc.

Another clever design element employed in the 500 Gamma chassis is the forged aluminium steering head, which doubles up as a home for the air cleaner, saving both space and reducing any unwanted induction noise.

The RG’s suspension was de rigueur for the time; 38mm air-assisted telescopic forks with adjustable preload and a hydraulic anti-dive system – or Posi Damp Fork to give it its slightly dubious moniker. Under braking – i.e. high compression load on the forks – the system generates a counter compression force within the forks to stop them from diving too far. Should the bike run over a bump during this time, the anti-dive force is released automatically allowing the fork to absorb the bump. While ingenious at the time, rapid improvements in damping control and suspension technology quickly rendered anti-dive systems obsolete.

The Gamma’s rear Full-Floater suspension was Suzuki’s secret weapon during the ’80s and by far the best rising rate single shock system on the market. The system, which mounts the shock and linkage independently of the frame and swingarm, provides progressively firmer damping throughout the shock’s stroke, aiding both rear wheel traction and ride quality.

To ride, an RG500 feels light, quick to turn (thanks to a lack of weight and a 16in front wheel) and able to change direction with ease. Although a race replica, the riding position is fairly relaxed and roomy, especially compared to an RGV250, although it is more focussed than both Yamaha’s RD500LC and Honda’s NS400R. The front damping quality although sophisticated in 1985, can feel crude and slightly choppy. What really holds the Gamma back, however, is its embarrassingly skinny tyres – 100/90 V16 front and 120/90 V 17 rear. Even 1990s 125s come with fatter, stickier rubber options. As a result, many owners upgrade the wheels to either RGV250 VJ22 of GSX600F, both offering 17in front and rear and the advantage of bigger, more powerful brakes too.

Suzuki RG500 (1985-1989) – What to look for

Engine
RG500 crankcases are line-bored, so you can’t mix or match tops and bottoms. If you lunch an engine and it smashes the cases, you’ll need a whole new engine. And finding one of those is getting harder and more expensive. 

Tuning
There are a plethora of skill tuners out there -both in the UK and abroad – who have expertise in getting more power from the RG engine. Stage 3 tuning, with pipes, a programmable ignition, uprated disc valves etc can see a genuine 130bhp at the rear wheel, but it comes at a cost. Pipes and a mild tune is better for reliability – and the pocket – and will take peak power to over 100bhp. 

Disc valves
Beware the internal lining on an RGs disc valves. It can break up, come away from the discs and enter the engine, leading to all sorts of expensive damage. If you’re intending on buying an RG that’s been unused for a while, it’s recommended to inspect the disc valves before starting the motor and using the bike. 

Carbs
Leaking carbs have long been an issue for the RG, even when relatively new. Sticking float valves are the issue. Higher flow float valves (available as aftermarket parts) reduce the issue. It’s worth cleaning the carbs of any RG that’s been stood, to remove any residue from old fuel. 

Lack of use
RGs always run better when used. Bikes from collections might make an appealing purchase, but an RG500 that’s been stood for long periods of time without use comes with its own issue. When stood, two cylinder intake are always open. This allows air to get inside the engine that can, over time, dry out the crank seals and/or cause internal bearings to corrode. Dry crank seals lose any inherent flexibility they once had, so the chances of them failing and allowing gearbox oil into the crankcases is high. Clouds of thick, white smoke are an obvious sign that all is not well. An engine rebuild is the only cure. Sticking piston rings, seized calipers and solidified brake fluid are other potential issues of non-use. 

RG400s
There’s nothing inherently wrong with the Japan-only RG400 (built because its lower capacity better suited Japan’s restrictive licencing laws), but values are far less than for the 500 because, a) its performance is much less – 59bhp compared to 95bhp, and b) the 400 can’t easily be transformed into a 500. Both bore and stroke are different, the clutch runs fewer plates and a shallower basket, and the big end bearings are smaller running one less roller.

Gearbox
An issue back in the day, especially with early bikes. Weak second and sixth ratios led to quite a few transmission failures, taking cases out in the carnage. Updated parts were fitted under warranty – bikes with engine numberm102120 onwards had them fitted as standard.

Bodywork
Good nick original panels are now like hen’s teeth. The factory seat cowl was offered as an option when new, so if you get one with a cowl fitted you’re already ahead. Bodywork fittings can crack/break, so check thoroughly. Likewise, fibreglass replica panels – they’ll be thinner and more fragile than OE.

Projects
With mint RGs making north of 20K these days, a cheaper project can look tempting. But buyer beware. Engine rebuilds can become horrifically expensive very quickly if you need barrels bored, new pistons, crank rebuilds, gearbox repairs or, god forbid, new crankcases. Missing parts can be hard to find, too, so don’t expect to pick up the bits you need at reasonable money down the local autojumble. At the very least, make sure what you buy is a runner.

Suzuki RG500 (1985-1989) – Rivals

1985 Honda NS400R - Gorgeous, beautifully engineered V3 two-stroke that although considered part of the Japanese 500GP replica class, is actually a big 250 in both engine a chassis. Fabulous handling, and still a buzz to ride, but lacks the RG’s bite and presence. Standard exhaust note is a big feeble too, but much easier on the pocket to buy than the Suzuki. 

1985-1987 Suzuki GSX-R750F-H - Suzuki’s original four-stroke race rep, the GSX-R750F was released the same year as the RG500. Light, fast, and exciting it shares much with the RG, but now even a mint Slabbie can be had for considerably less money than an RG. G and H models benefitted from chassis tweaks and engine updates that improved stability, handling and reliability. 

1984 Yamaha RD500LC - A tribute to Kenny Roberts and Eddie Lawson, the RD was a revelation back in 1984. But in reality the 500LC is just a big pussy cat. Very flexible and torquey in delivery, it’s actually a really decent road bike – if you can afford the fuel bill. Not as sharp as the RG, or as jewel-like as the NS. Damn expensive, though. RZV500R has an aluminium chassis, but a touch less power.

Honda NS400R, 1985 | Approx. Price: £6000-£12,000

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Power/Torque

72bhp / 39lb-ft

Weight

163kg

Suzuki GSX-R750, 1985-1987 | Approx Price: £2500-£6000

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Power/Torque

100bhp / 52lb-ft

Weight

176kg

Yamaha RD500LC | Approx Price: £12,000-£20,000

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Power/Torque

88bhp / 48.4lb-ft

Weight

180kg

Suzuki RG500 (1985-1989) – Verdict

Suzuki’s RG500 Gamma is the best Japanese 500GP replica, no question. It’s the fastest, most powerful, most exciting to ride, easiest to tune, and closest to its race bike inspiration. But in comes at a price. Other than Bimota’s ill-fated V-Due 500 twin, there is no other more modern 500 2T to choose from, so asking prices for these square-four Suzukis are now astronomical - £20,000-plus buys a lot of other desirable machinery. If it has be a big two-stroke, however, there’s no better…

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Suzuki RG500 (1985-1989) – Technical Specification