1984 Yamaha RZV500R

1984 Yamaha RZV500R

Back in 1984, Yamaha launched on an unsuspecting public what was touted as a Roberts/Lawson twostroke V4 YZR500 GP racer with lights, badged in Australia as the RZ500. Regretfully, it wasn’t really that at all, more the coupling together of two RZ250 parallel twins on a common crankcase to create a reed-valve twin-crank 50-degree V4 (the GP racer had rotary disc induction), but it nonetheless quickly became a cult classic.

Production lasted for only two years, with just 8000 units made, roughly split between the steel-framed 205kg 78rwhp RZ500 sold in Europe (as the RD500LC), Canada and Australasia, and the alloy-framed 196kg 64rwhp RZV500R sold only in Japan. 

The United States didn’t get either, on account of their more stringent pollution regulations, which didn’t sit well with Major Wyn Belorusky, a 500GP tragic who was for a time posted to a US Air Force base in Japan. “I’d been biking since my mid-20s, but when I got posted to Okinawa I sold my 900 Ninja because I knew I was going to buy a two-stroke Yamaha as soon as I got there,” says Wyn. “It’s a dare-to-bedifferent bike that back then was forbidden fruit for us Americans. And being 6'3" tall (1.90m) and weighing 240lb (109kg), I was automatically disqualified from riding a 250 or 350. So it had to be the V4!”

Back home in Florida three years later, Wyn set about concocting the ultimate GP racer-with-lights out of a late-1985 RZV500R that he aimed to turn into the closest thing to a 500GP bike you’ll ever see on the street, accomplished with the aid of his friend Steve Cisewski. “I can come up with the ideas and fabricate the parts, but I can’t weld,” says Wyn. “Steve glues the parts I make together. We’re a good team.” 

First objective was to stiff en the stock chassis to handle more power and extra suspension loads, as well as to achieve the Deltabox GP look that was Wyn’s objective. This meant adding an extra aluminium box-section frame spar beneath the original one to double up on depth, milled and welded to look as if was born that way, and coated with high-impact black paint. Steering head and rear engine mounts were all reinforced, the rear sub-frame is now detachable, and the frame cleaned up with the removal of unnecessary tabs. A 1994 Suzuki GSX-R750 swingarm was modified to operate the RZV500R’s original Öhlins shock, shortened 20mm to retain the original 1375mm wheelbase and ‘bananaised’ to allow both exhausts from the lower pair of cylinders to exit side by side on the right, just like on the GP bike.

A ’96-model GSX-R750 donated the fully-adjustable upside-down 43mm Showa fork (in place of the 37mm conventional fork fitted originally), now housed in billet aluminium triple clamps machined from solid by Wyn himself, and fitted with a titanium stem, while maintaining the original RZV500 steering geometry of 26° rake and 95mm of trail. To replace the skinny 16in-front/18in-rear period wheels, Belorusky sourced a pair of 17-inch cast aluminium Marchesinis — the rear a much fatter six-incher — fitted with D207 Dunlops and running on titanium axles from New Jersey-based Yoyodyne, who also supplied the 190mm titanium rear brake disc. Front brakes are British-made PFM cast-iron rotors gripped by the GSX-R750’s six-piston Tokico calipers (rear is a Brembo), while the bike is littered with numerous examples of Wyn’s fabrication expertise and attention to detail. These include the carbon-fibre dash, rearset hangers and rear brake foot lever, plus titanium footrests and aluminium gearshift pedal, assorted spacers, rear brake torque arm and clutch and brake hand levers all machined from solid billet, and matched by TZR250 switchgear and throttle assembly. 

The completed bike is clothed in a set of carbon-fibre bodywork sourced from the Team Roberts moulds for Wayne Rainey’s 1991 YZR500, fitted with a pair of 55-watt headlights, and matched by a carbon-fibre fuel tank with an integral oil tank for the separate oiling system. Liberal use of exotic materials and a ruthless approach to removing unnecessary metal enabled Belorusky to slash the dry weight of the complete bike to just 134kg. “I figure there’s over 100lb of motorcycle somewhere in my trash can!” Wyn laughs. Or to make another comparison, that’s just 4kg over the final minimum weight limit for factory 500GP race bikes! 

To deliver power to match, Belorusky enlisted the help of engine tuner BJ MacDonald to bump the stock Japanesemodel RZV500R’s power output from 64rwhp at 9500rpm to something over 100rwhp at 11,500rpm in its current guise. This involved porting the V4’s cylinders — which still retain the stock YPVS powervalve system — reshaping the heads and recutting the squish bands, retiming the stock ignition, then fitting a quartet of 28mm Mikuni flat-slides to replace the 26mm stock items. These are surmounted by K&N filters in feeding each cylinder through 90° intake manifolds, and thence via RD/RZ350LC reed cages modified by Kevin Cameron and fitted with TDR reeds. A set of race-type expansion chambers are fitted, two each by rival Florida exhaust specialists Harry Barlow (uppers) and Brian Turfrey (lowers), but with the four silencers and billet alloy flange mounts all Wyn’s work. 

So how does it go? Well, for someone fortunate to have tracktested a fleet of mid-’80s factory 500GP racers, riding Wyn Belorusky’s highly modified RZV500R represents both a trip down memory lane and a what-if window on today’s sports bike scene, so sadly devoid of two-strokes. What’s most noteworthy, and surprising, is that Wyn’s weapon should be so well-mannered, usable even, at road-legal speeds — and remember that in the USA, that means 35mph (56km/h) in lots of places and a top limit of 75mph (121km/h) on freeways and four-lane highways. Perhaps because of that, Wyn has geared the bike down to pull just 130mph (209km/h) at redline, confirmed by the Avocet 45 bicycle speedometer improbably mounted to the dashboard (complete with carefully fashioned external reading lamp — you must be able to see it at night to get that Florida licence tag!), which registered 107mph when the race-style ’80s tacho measured 9500rpm. Mind you, I’d like to know when and where a cyclist hit that sort of speed without peeling the tyres off the rim, or launching off the side of a mountain! 

As expected, the result is truly impressive acceleration by any standards, and especially for a street-legal sports bike with full road registration. That said, the fact that Florida has no roadworthy inspections is presumably very helpful! “I couldn’t have got a tag for this bike in California,” admits Wyn as he handed me the keys. “They have too many unnecessary rules out west. Florida is the land of the free! Go cruise!” Yessir, Major, sir. Only obeying orders! 

Wyn’s Yamaha feels just like a late-’80s GP racer to sit on, albeit smaller than most of the final generation of four-cylinder 500GP bikes, in turn reflecting the greatly reduced amount of power its aluminium twin-spar chassis is called upon to put to the ground. It feels very light and quite compact, though the footrests are very high, reflecting the grip level delivered by the D207 Dunlops which stick far better than GP slicks did back in the day! Kick-starting the beast (there’s no electric leg) is an acquired skill, but once you get the hang of it, it’s easypeasy, though I’ll admit to just one run-andbump push-start, just like on an early-’80s GP grid, when I flooded it one time and decided jumping up and down on the lever in 85°F (30°C) Florida sunshine was not conducive to perspiration-free riding! 

The clutch lever seems a bit stiff at first, mostly due to Wyn shortening it to save some extra grams (“Never mind the pounds,” he says, “just worry about the ounces!”), thus reducing the leverage ratio somewhat. This only matters when downshifting, because the snick-snick gearbox action is otherwise plenty crisp enough to pretend you’re a GP racer and speed-shift without the clutch, in which case you can start to reap the benefits of Belorusky’s tuning talents. The Yamaha is improbably tractable and easy to ride in town, pulling cleanly off the fast 1500rpm idle with hardly any clutch, and accepting full throttle from as low as 2500rpm without coughing or snatching the drive train. The Mikuni flat-slides are perfectly set up, making five-minute sprint races to go get the milk, or 20-minute GP rides to the local McDonalds, as easy as on a scooter or roadster. Well, engine-wise, that is. The racelevel riding position, with the dropped bars and quite a lot of weight on your forearms, plus the pathetic steering lock and poor lowspeed handling make this a bike you’ll want to push through Ronald’s service line, rather than drive through! 

But then head for Racer Road for a postprandial blast, hook down some gears, dial up some throttle and prepare to be impressed. There’s an extra dose of revs when the power-valves crack fully open at 6000rpm, then from seven grand you’ve got serious acceleration on tap. But it’s not an explosive kind of power that sends the back wheel scrabbling, just a suddenly much stronger appetite for extra revs, which you’re eager to satisfy. Zapping through the ratios as you accelerate out into the Florida flatlands delivers performance that’s genuinely addictive. More, please, then more again! 

The reason a mere 100rwhp motorcycle gives you such a thrill is of course because of its light weight, which also pays off in the way it handles. The Showa fork and Öhlins suspension are quite stiffly sprung, but the damping rates are well chosen for such a light bike in street use. So while the Yamaha will skip over a traffic stud or road ridge on the angle, and briefly shake its head before resuming normal service, it rides bumps in the road surface well, and feels pretty compliant and well balanced in terms of response. The fact that the RZV’s steering geometry is more early-’80s than late-’90s means it’s not too radical, and arguably all the better for that in street use, turning in quite controllably to the few tight bends I could find. The Yamaha’s pretty stable under the heavy braking those great castiron front discs deliver — they have so much feel, and are easy to just finger lightly to get rid of excess speed. If anything, the whole chassis feels like it could handle even more power and performance in its stride. 

For this is that very unusual thing, a power-up project bike that’s as dynamically effective as it’s lovingly assembled from leading-edge hardware chosen for its capacity to impress. This is not just a collection of nice parts that’s all glitter but no go, but a carefully developed, progressively refined entity that is honestly the closest thing to a road-legal 500GP racer I’ve ever ridden. 

ENGINE Water-cooled two-stroke 50-degree V4; twin contra-rotating crankshafts with gear-driven balancer; reed-valve induction, with four transfer ports and a single exhaust port; 54 x 54mm for 494cc; 4 x 28mm Mikuni flat-slides; Yamaha CDI ignition; YPVS powervalve exhaust with expansion chambers; geardriven primary to oil-bath clutch and six-speed cassette gearbox; chain final drive; 100+rwhp at 11,500rpm (est)

CHASSIS Aluminium twin-spar mainframe with detachable sub-frame; fully adjustable 43mm USD forks, 2 x 320mm PFM cast-iron rotors with Tokico six-piston calipers on 17 x 3.5in Marchisini alloy wheel; modified GSX-R aluminium swingarm with Öhlins monoshock, single 190mm Yoyodyne titanium rotor with Brembo twin-piston caliper on 17 x 6in Marchisini alloy wheel; Dunlop D207 tyres

BODYWORK Carbon-fibre YZR500 fairing, tank and seat; hand-fabricated controls; TZR250 switchgear; Avocet bicycle speedo 

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