At the lower speeds these bikes are civil, almost disappointingly so. You’d expect them to be frisky and unmangeable, but not a bit of it. Solid, torquey pull from zero revs. The RG’s rev counter doesn’t even start until 3,000rpm but it’s pulling handily even before then, while the RD500 is very civilised despite all the noise from its four stingers. So we crackled off up the road, engines warming and imagining ourselves as our GP heros.
Out on the open road and time to let ‘em rip. What a difference in character. Jim was giving the RG a big handful when it hit the powerband at 6,000rpm and went vertical on him. It wasn’t a pleasant affair. The RG gets into its stride and goes beserk by hitting an incredibly sharp power step. It’s literally doubling its power in just 2,500rpm from 35bhp to 70bhp, and if you’re not ready you get an instant upward lunge that isn’t that easy to control. Get your clutch control right at the RG500 will steam the quarter-mile in 11.1 seconds at 120mph, but be aware it’s coming. No mincing about, no soft hits, but proper speed and power. The exhaust note hardens and you get a real rush as the powerband kicks in with aggression that no four-stoke can match. Then at 8,500rpm it’s over until you get the next gear in. The RG is equipped with a beautiful gearbox, so give it the next gear and let it all happen again. This is real speed and 130mph comes up indecently quickly on the right (fairly straight) roads.
By comparison the RD500 is a touring engine, lumps of easy midrange power between 3,000-7,000rpm that is more accessible than the Suzuki, but certainly not as exciting. It’s longer (by 20mm) and 25kg heavier, and this is reflected in the way the Yamaha feels to ride. On tighter roads the Yamaha is the faster bike simply because you can use more power, more of the time. It’s not doing it’s level-best to kill you, and the handling is far more refined on the V-4. The RD500 is very stable in the corner; the enormous 120-section front tyre means the steering is never going to be quick, but there’s plenty of feel from the front end. Get a rythm going and the RD can be hustled through the corners. The square-four shrieks and yelps, the V-4 digs in and grunts. But I much prefered the thrill of the Suzuki, I want my GP replica to scream, have a killer powerband and excite me.
As the Yamaha chases the Suzuki through Kent the differences in engine character and handling make themselves even more obvious. The RG tends to skitter and hop from firm, under-damped suspension while the RD is more prone to spit at you through the handlebars. Buyers of the Suzuki might want to seriously think about investing in a steering damper, she can certainly get skittish! And that’s when the Yamaha starts scoring points. Regardless of their heritage and styling, we aren’t on a race track here. Which is a good thing because the RD’s brakes aren’t very impressive.
I know two-stroke racing is all about corner speed, but the Yamaha’s twin piston calipers are really lacking in power. You need a good four-finger squeeze on the bar, at which point you can feel the anti-dive doing its job. By comparison, the RG’s four-piston caliper set-up is straight off the racetrack and much sharper. All you need is two fingers and the Deca brake system hauls you down in no time. The forks on the RG aren’t as sophisticated as those on the Yamaha (maybe it’s because there’s less weight over the front) and hitting bumps under full braking unsettles the Suzuki where the Yamaha will track straight and true.
Cutting edge two-stroke tech
Both bikes offer serious levels of technolo gy for your money. The RD’s 50˚ V-Four has twin cranks geared together, with a counter balancer too. On the 0W-70 racer the carbs live between the vee, but on the RD the powervalve mechanisms are in the way so the 26mm Mikuni carbs are side mounted, breathing fuel into the engine via inlets that turn 90˚. Makes them easier to work on. And for the same reason, while the forward cylinders are fed through the cylinders, the rear cylinders are crankcase fed.
Because of the rear facing high-level exhausts, there is no space for a conventionally mounted shock, so the Yamaha’s shock is under-slung with the front mounting on the crankcases. It’s a curious set-up and means the shock gets hit by huge amounts of road dirt, needing careful looking-after.
The RG is more faithful to the RG racer, though, mimicking the square-four architecture so faithfully that it takes an educated eye to tell the difference. Again it’s a case of two twins, two cranks, geared together. This time matched to a cassette-loaded gearbox – very advanced. Rotary valve induction gives the sharp purposeful power characteristics and rotating exhaust power valves allow a modicum of midrange. The chassis is a work of art. Aluminium, it features pressure castings for the headstock (which also serves as an airbox) and swingarm pivots with square section extruded tubes. The rear shock is squeezed by Suzuki’s excellent Full Floater set up which meant both ends of the shock are pivoted by connecting links and squeezed at once.
Renowned two-stroke tuner Stan Stephens confirms the RD and RG are very different personalities.
“The RD is a road bike. A good one, stunning to look at, but a road bike. With reed valve induction and powervalves, it is designed to produce soft and tractable power. The marketing blurb might liken it to the GP racers (Eddie Lawson’s OW-76 of 1984 was a twin crank motor with reed valve induction) but you can tell from the engineering where it comes from.
The RG is properly derived from Suzuki’s race bike. There are many similarities and both the disc valve induction and on-off exhaust valves mean the RG has all or nothing power delivery. I think it’s fair to say Suzuki have done it properly. With some careful tuning work we’ve seen 94bhp at the rear wheel on our dyno. It’s a very serious proposition.”
James Whitham has ridden both bikes and the RG is “his own” (a Whit-euphemism for Suzuki GB owned, on long and loose loan). “There’s absolutely no fookin’ comparison – as a road bike the RG is miles better. The Yamaha came out earlier and to look at it, it looks like a real GP bike. If you’d never seen a GP bike up close. It’s beautiful, but to ride it’s really disappointing. It’s all about midrange plonk and steady handling on the Yamaha, whereas the RG will have wheelied sideways into the gutter on the way out of my drive. The RG is a bit more workman-like to look at, but when ridden there is no comparison.
I’ve had some pipes put on it and it can really go. It can only make about 80bhp but it feels more like 200bhp. I like that about two-strokes, they make a little feel like a lot. Mind you, you have to pay for it. When I go over the moors I have to stop at every petrol station, you can never bank on the tank lasting the distance if you try for the next. It’s fuel every 45 miles!”
Rampant race refugees
For GP replicas you’d expect these two bikes to make a huge impression on the racing scene, but it hasn’t worked out like that. As Stan Stephens explains, in production racing they’ve been placed in a class of up to 750cc four-strokes.
“The RG suffers badly because the starts in Formula One are dead-engine, and the RG can’t be started in gear. You have to have it in neutral, left foot down, right foot on the kickstart. Then when the lights have changed you get it started, put your right foot down and get your left foot on the gear lever. By the time you’ve gone through all the foot swapping the GSX-Rs and FZs are halfway to Druids! That said an RD500LC did win the Australian Castrol Six-Hour production race in 1984.
The RG has stolen its own competition kudos by way of the British Formula One championship. James Whitham races in this series and describes the rules as “mental – you can chop the bikes about as much as you want!” And so Padgetts, the Yorkshire two-stroke race specialists, have built an RG based on the road going RG but using RG race parts. The result?
“Fookin’ hell it is trick.” says Whitham. “Such a tuned motor and it weighs probably no more than 125 kilos when us, on the 750s, are struggling around the 170 mark.” Clive Padgett confirms that their RG500 did 171mph at Hockenheim.
The RG500 is a rampant race refugee while the RD500 is a refined roadbike. For sheer character we’d take the Suzuki over the Yamaha without a second thought. But only time will tell if these two strokers are any more than a flash in the pan.
