Any MO readers over the age of 40 probably have fond memories of watching Wayne Rainey make his magic happen on the best-looking 500cc Grand Prix bike ever built – the Marlboro Yamaha YZR500. His first championship year, 1990, was one of the most memorable seasons I can remember. I was 15 and still remember those late nights staying up to watch the races. By the time I was 16 I had an old blown-up RZ250FN and big plans to paint it up in Marlboro colors. I had the posters and the dreams to go with them!

Wayne Rainey riding a Yamaha YZR500, circa 1991.

The YZR500 first debuted in 1973, and the bike went on to amass 115 wins and 11 world championships in its amazing 30-year history. Nearing the end of its run at the turn of the century, the YZR was spitting out around 200 horsepower in a machine weighing just 286 pounds, the category’s minimum weight.

Meanwhile, my motorcycle path took me into an apprenticeship as a motorcycle mechanic at Len Willing Motorcycles, brother of Warren Willing, the man behind the winning Marlboro YZR500s and, later, Kenny Roberts Jr.’s world title. I’d hear second-hand stories from Len after each GP, and from that time on I was hooked on YZR500s and I still am.

So when Mick Costin, proprietor of Costin Engineering, called to let me know there is an opportunity to ride his ‘best’ build yet – a 1990 YZR500 Rainey Replica – I jumped at the chance.

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I arrived at Eastern Creek Raceway (Sydney Motorsport Park) to find the bike being warmed up and I almost lost my mind. There was a large crowd building around the bike, and as chance would have it, 500 GP legend and ex-Wayne Rainey teammate Kevin Magee was one of the onlookers. He also commented that the bike is exactly the same – a perfect job. We offered him a ride on it, and he jumped at the chance, but a piston failure prevented any of us from riding the bike that day. However, we did get to strip it and shoot it and have a chat with Mr. Costin.

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This was a customer build with a good budget that allowed Mick to truly replicate the 1990 machine. This meant a lot of time and effort on tooling to reproduce the frame, swingarm, engine mounts, fairings and to make an RZ500 streetbike engine look like a YZR500 engine.

“The dimensions are exactly the same as the 1990 bike,” says Costin. “The only difference is the position of the engine mounts to accommodate the different crankcase shape and mounting positions on the RZ engine. The frame was a huge task. The tooling to press the indents on the side beams and into the swingarm alone was a big job. The three pressing tools had to be made of carbon steel, and it was a mammoth task pressing those sections up.”

The frame is exactly the same as the original. In fact, Kevin Magee could not pick the difference between this bike and the original 1990 YZR that he raced.

The frame is exactly the same as the original. In fact, Kevin Magee could not pick the difference between this bike and the original 1990 YZR that he raced.

The frame is made of 6061-T6 alloy sheet and billet, which is heat-treated after welding, giving the material maximum strength. Once finished it was painted black.

Costin Engineering triple clamps squeeze ex-Christian Sarron 1990 YZR500 Öhlins forks that are anodized black. The handlebars are original 1990 YZR500, and the Öhlins shock remote preload adjuster is mounted on the top clamp as Rainey had. The swingarm is identical to the 1990 YZR500 and has an original 1990s-era YZR500 Öhlins shock controlling it. The wheels are original 1990 YZR500, as are the brakes.

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Ohlins original 1990 YZR500 shock with Costin Engineering ride height adjusters and remote preload adjuster.

“The wheels are so light,” says Mick. “I have some 1990-era forged alloy wheels, and the YZR500 ones are 30% lighter again. No wonder they had limited mileage. They weigh the same as the brake rotors!”

Costin says the brakes are 1990 YZR500 Nissin rotors with Nissin YZR500 calipers, while at the back a captive quick-change set-up Brembo caliper is fitted along with a YZR500 rotor. As per the Wayne Rainey 1990 bike, there is a radial-pull AP master cylinder fitted as well.

The replica uses the same front wheel, forks, rotors and calipers as the original 1990 YZR500.

The replica uses the same front wheel, forks, rotors and calipers as the original 1990 YZR500.

The engine is a highly modified RZ500 unit. It has vapor blasted, machined and water-cooled crankcases, RZ Performance crankshaft and conrods, Mitaka pistons and rings, Costin Engineering cylinders with individual power-valve controllers and YZR500-style water jackets, and modified TZR250 3MA SP cylinder heads. A Costin Engineering cast clutch cover is used, while the actual clutch is a highly modified TZ350 unit. An extended input shaft allows the dry clutch conversion and the oil pump system is removed, with a cast magnesium cover giving the GP look. An electric water pump is employed, and the radiator is a Costin Engineering item, with a TZ250 water bottle used.

Mick has done an amazing job making the RZ500 engine look like a YZR500 engine. Cylinders are split along with heads and bead blasted to aluminum finish.

Mick has done an amazing job making the RZ500 engine look like a YZR500 engine. Cylinders are split along with heads and bead blasted to aluminum finish.

Rainey’s bike ran steel expansion chambers for most of the 1990 season, aside from a few races at the end where titanium items were used only for the top two pipes. In keeping with the original, Costin made four steel expansion chambers, which are stunning. They all have original YZR500 mufflers.

The upper pipes, like the lower, were hand made by Mick in the same mild steel that the original was.

The upper pipes, like the lower, were hand made by Mick in the same mild steel that the original was.

The ignition system is a Costin GP plug-in race system with adjustable ignition curve and power-valve controller. All electrical components are mounted up front as per the real bike. Fueling is taken care of by four 28mm Mikuni flat-slides.

Finishing the bike off is the stunning bodywork, which is original YZR500 painted the traditional colors.

The fuel tank is made by Mick as well.

The fuel tank is made by Mick as well.

I’m sure you agree, the bike sure touches on some great memories of the true GP heroes on the wild 500s, with Wayne Rainey being the master of the YZR500.

The Ride

I was fortunate enough to test a Costin YZR500 on another occasion, and although the engine was brand new and not run in, I still had a ball on the bike. The engine was tight so I did not use it to its full potential, but what I did use was more than enough to have me carrying good momentum around the testing facility.

Mick Costin take the Rainey replica on its debut run at Eastern Creek Raceway. Sadly the Mitaka piston broke shortly after.

Mick Costin take the Rainey replica on its debut run at Eastern Creek Raceway. Sadly the Mitaka piston broke shortly after.

The first thing I noticed was how real the bike feels. I’ve ridden my share of TZ250s, RS250s, and also an ex-John Kocinski Cagiva 500cc GP machine, a bike that was virtually a copy of the early YZR, and this replica has the real-deal feel about it.

Tested: Cagiva V593 500cc Grand Prix Racer

It stops like a GP bike, turns like a GP bike and is absolutely on rails. The chassis is ultra stiff, giving that knife-edge snappy feel of a GP thoroughbred, and it carries fantastic corner speed.

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Tucking in down the chute had me grinning – the four genuine YZR baffles howling and the STACK tacho climbing rapidly as the front wheel lifted over the crest. I felt like a real GP rider! An amazing ride that I’ll remember for a long time…

Wayne Rainey

Rainey needs no intro to MO readers. The legend’s career began in the AMA Grand National Championship, a series that encompassed dirt-track disciplines plus road races. In 1981, Rainey finished the Grand National season as the 15th-ranked dirt-track racer in the country. Following his success in the Novice 250cc roadrace class, Kawasaki hired him to compete in the 1982 AMA Superbike Championship as a teammate to the defending National Champion Eddie Lawson. The following year, Lawson moved to the Grand Prix circuit and Rainey took over the role of leading rider, earning the 1983 Superbike championship for Kawasaki.

In 1984, he accepted an offer to ride for the newly formed Kenny Roberts Yamaha squad in the 250cc class of the Grand Prix World Championship. A less-than-successful season saw him returning home in 1985 to join the Maclean Racing team in U.S. 250 and Formula 1 classes, and then onto the American Honda team from 1986 to 1987 where he raced Superbike and F1. It was during the 1987 Superbike National Championship that his intense rivalry with Kevin Schwantz began, as the two battled it out for the title. Rainey won the championship, but the fierce rivalry between the two competitors was just beginning.

MO Interview: Wayne Rainey

In 1988, Rainey returned to Europe, again joining Team Roberts Yamaha, this time in the premier 500cc division riding the YZR500. In the 1989 campaign, Rainey finished runner-up to Lawson. From 1990 to 1992, Rainey hit his stride and earned three consecutive 500cc crowns for Yamaha. Rainey was well on his way to his fourth-consecutive title in 1993, leading the championship when he suffered his career-ending crash at the Italian Grand Prix in Misano. He slid into the gravel trap at high speed, breaking his spine against the raked surface designed as a safety feature for car racing. The injury handed the title over to his great rival, Schwantz. Rainey’s injuries rendered him permanently paralyzed from the chest down.

After turning to Williams Formula 1 team owner and quadriplegic Frank Williams for advice, Rainey later became the team manager for Marlboro Yamaha for a few years.

Wayne Rainey speaking with Max Biaggi ahead of qualifying for the 1999 Japanese Grand Prix at Motegi.

Rainey lives in Monterey, California in a house built near the Mazda Raceway Laguna Seca circuit shortly before his career-ending accident. Rainey was inducted into the AMA Motorcycle Hall of Fame in 1999. The FIM named him a Grand Prix Legend in 2000, and he was inducted into the International Motorsports Hall of Fame in 2007.

Wayne Rainey Interview: Inside MotoAmerica

After fading from the motorcycle racing scene for several years, Rainey and the KRAVE Group took over American Superbike racing from the AMA and Daytona Motorsports Group in 2014, launching the MotoAmerica series in 2015.

Yamaha YZR500 Wayne Rainey Replica Specifications
Engine 1985 Yamaha RZ500 V-4 two-stroke
Bore and stroke 56.65mm x 50.0mm
Compression ratio 6.6:1
Components RZ Performance crankshafts and conrods, vapour-blasted stock crankcases converted to water-cooled cases, stock ported and polished cylinders, machined TZR 3MA SP heads, balanced Mitaka forged pistons and rings; Costin Engineering magnesium oil pump cover, independent power-valve actuators, Boyesen reeds, four 28mm Mikuni flatslide carburetors, Costin Motorcycle Engineering expansion chambers, YZR500 mufflers.
Power 105 rear-wheel horsepower
Transmission Factory six-speed cassette-style gearbox with extended input shaft
Clutch Dry conversion TZ350 clutch, Costin Engineering clutch cover.
Miscellaneous All bolts machined stainless steel or titanium, Costin Engineering radiator, electric water pump, custom black box incorporating programmable CDI ignition, programmable power-valve controller, quad coils, 15/36 gearing.
Chassis Costin Motorcycle Engineering replica 1990 YZR500 frame handmade from 6061 billet and sheet alloy, matte-black finish, 1990 YZR500 replica swingarm
Front Suspension 43mm Öhlins original YZR500 forks
Rear Suspension 1990 YZR500 Öhlins shock with custom linkages and Costin ride-height adjuster and remote preload adjuster
Front Wheels 1990 YZR500 alloy 3.5 x 17-in. wheel
Rear Wheels 1990 YZR500 alloy 6 x 17-in. wheel
Front Brakes YZR500 1990 Nissin 320mm rotors with four-piston YZR500 1990 calipers
Rear Brakes 210mm YZR500 rotor with Brembo TZ caliper, AP radial master-cylinder
Bodywork 1990 YZR500, 1990 YZR500 seat, YZR500 replica custom fuel tank, YZR500 front guard, billet alloy fuel cap.
Weight 276 lbs (claimed) wet

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  • Sean Bice

    Amazing work to replicate Wayne’s 1990 YZR500 OWC1! I just have a couple of things to point out. 1. In the photo caption where it says, “Wayne Rainey riding a Yamaha YZR500, circa 1988”, that photo was actually taken in 1991, and Wayne is aboard the 1991 YZR500 OWD3, which is Wayne’s (and my) all-time favorite Yamaha for several very specific reasons! 2. I’m curious about the RZ500 engine that was used. In stock form, that engine had the four stock Mikuni carburetors placed on each side of the engine in a disc-valve layout (even though the engine was reed-valve-inducted), but the carburetors on this replica appear to be placed in the “vee” of the engine just like the carburetor placement on the works OWC1. How was that very critical modification to the RZ500 engine accomplished? 3. An unusual fact about the RZ500 and the YZR500 was that the engines were actually not V4 configurations, but more accurately, they could be described as “W4” configurations due to the fact that they featured two counter-rotating crankshafts (one crankshaft for each bank of two cylinders).

    • denchung

      Thanks for clarifying the year of photo. We were working with the information Getty Images provided which was more an estimate.

      • Sean Bice

        No problem. I’ve used that same photo from Getty myself, and I remembered that they had the year wrong for it. Same for the other Getty photo of the OWD3. It very well could have been taken at Donington Park, but it would have been sometime on August 2-4,
        1991, and not on April 7, 1984, as they have the photo captioned.

        • Kevin Duke

          Wow, how lucky are we to have your expertise, Sean – thanks! The carb arrangement on a stock RZ was very complicated, as you indicated. I’ll see if I can get the author of the story to explain how Costin could get them inside the vee. Speaking of vees, I’d say the RZ/YZR engines are V-4s, as that’s the arrangement of the cylinders, even if the front and rear cylinders aren’t linked to a common crank. Semantics… :)

          • Sean Bice

            Thanks, Kevin! I’m definitely no expert, but I do love Wayne and those YZR500s. And, yes, I agree with you that they are V4s…just a little “did you know” with the twin cranks. Also, I suspect that the tortuous route that air had to take to get into, and through, those side-mounted Mikuni carbs on the RZ500s was due to emissions, the size of the airboxes required, or both. It was the second-strangest thing on that bike. The first-strangest thing being the odd, underslung shock that sat horizontally below the engine! Just a couple of idiosyncrasies that made the RD/RZ500s so unique and special.

          • Kevin Duke

            I share an affinity for the RZ500, as that was the first streetbike I ever owned. Damn, I miss that thing!

        • Kevin Duke

          Okay, Jeff Ware finally stopped riding cool bikes long enough to reply about the carb setup! “Hi Sean, glad you liked the article and the bike. The carbs are still mounted in the original side positions, however, remade intake manifolds take them closer to the engine. You can just see them under the main frame rail. Cheers mate.”

          • Sean Bice

            Thank you, Kevin…and Jeff! Again, fantastic job on a very cool bike!

  • Wayne Nagata

    I was in love with this bike too; ) Way back then I managed to buy a new Yamaha domestic (Japan) RZV500R V4 two stroke street bike. It was a replica of the much earlier versions for their F1 bikes. It was very fast for it’s time, I could pull GSX750s and stay even with the GSX1000s. Sadly I seized a cylinder, never repaired it and sold it as a roller 5 yrs ago. What a bike and what a thrill to ride it; ).

  • https://ffrf.org/ QuestionMark

    Just a beautiful piece of work from a wonderful era of racing.