[Custom Machine Introduction] The exterior is the real deal! A real replica of the Suzuki GP500 machine, the RGV-γ [Kentsu Sports RG500 Gamma]

KENZ SPORTS in Misato City, Saitama Prefecture, has created a fully customized Suzuki RG500 Gamma. This is the fourth custom 500 Gamma built by the shop. They have managed to fit genuine parts from a works GP500 racer onto a commercially available motorcycle with a different frame structure, achieving a seamless form and finish that belies the modification. This machine is a testament to the owner's passion for the Gamma and KENZ's custom design sensibility.

A Sense of Craftsmanship that Drapes a Production Bike in the "Authentic Aura of a Works Machine"

KENZ SPORTS RG500γ

KENZ SPORTS RG500γ

The fairing mounted on this custom RG500 Gamma is genuine, from the 1988 Suzuki GP500 machine, the RGV-γ (XR74). These are treasured parts of KENZ SPORTS representative, Kenzaburo Kawashima, who has a long history of racing with Suzuki motorcycles.

KENZ has previously built custom 500 Gammas replicating the Suzuki works GP machines of the 1980s, such as the Herve and Pepsi liveries. This is their fourth such project. While faithfully reproducing the V4 engine XR74's style, the coloring is inspired by the square-four engined GP500 machine, the RG-γ (XR45), ridden by Katsumi Mizutani at the 1983 Japanese Grand Prix. This unique and enthusiast-focused collaboration is a distinctive feature.

It goes without saying that the KENZ-treasured XR74 fairing is key to this. However, the production RG500 Gamma has a frame shape that is completely different from the GP machine, so simply attaching the fairing would not recreate the XR74's authentic atmosphere. Even a slight change in the angle of the tail cowl, for instance, can lose the essence of an 80s racer. To achieve that "genuine feel," adjustments in the millimeter range are necessary.

With this in mind, take another look at this machine. Suzuki GP machine enthusiasts will undoubtedly grin, but even those less familiar will see it as a flawlessly executed, incredibly cool GP500 replica. Fitting fairings from different models and perfectly recreating the intended atmosphere – this balance and meticulous historical research into the parts used are the machine's greatest appeal and, as Kawashima emphasizes, the very essence of KENZ's expertise.

The right side is packed with highlights, including the two front-bank expansion chambers routed to the right and the curved swingarm that accommodates them. The atmosphere is that of a works GP machine, but the ability to evoke this on a production Gamma with completely different dimensions and frame geometry is KENZ's true forte.

While the overall form replicates the V4 engine RGV-γ, the coloring is from the square-four RG-γ. This is a custom build that truly embodies "a machine for the owner." The model name on the fairing is "RG γ" despite the V4 engine motif, for this very reason. The slight bluish tint of the white on the fairing and wheels is a detail based on examination of the actual machine.

The front view is exactly like a works racer, and the four silencer ends create a very racy rear view. Of course, it's street-legal, and the minimal installation of safety equipment that doesn't detract from the racer's atmosphere is also a skillful touch!

Full Reproduction of the Works GP Racer, RGV-γ

The Suzuki GP500 machine, the RGV-γ, raced by K. Schwantz and R. Mamola in 1988 with Pepsi sponsorship. The XR73 (photo below) was used in the first half of the season, while the improved XR74 was introduced in the latter half. This XR74 featured a revised exhaust system with the front two cylinders' expansion chambers changed from dual outlets to a right-side dual exit, and a curved swingarm.

Please take a close look at the two machines and compare their atmospheres!

A Custom Bike You'll Want to Admire in its Stripped-Down State

While almost everything except the frame and engine has been changed on this machine, a notable component hidden beneath the fairing is the monocoque-style seat rail. This was also designed with the XR74 in mind, fulfilling the owner's desire to "want to admire it stripped down, with the fairing removed." KENZ responded to this request.

As you can see, this is a custom-made part, meticulously crafted from individual aluminum sheets and welded together, including the fuel tank stays. It is a labor-intensive and costly piece, and its finish is superb. It truly symbolizes the character of this machine. It also houses a custom-made aluminum oil tank and, fitting for a street machine, an ETC (Electronic Toll Collection) unit.

The normal seat rail is welded to the main frame. This has been cut and the seat rail rebuilt in two pieces: the front part supporting the rear of the tank, and the rear part bolted to it, supporting the oil tank and rear safety equipment. The organically curved pressed aluminum sheet and the lightening holes on the top surface exude a custom-made feel!

The request to "want to admire it stripped down" is quite niche, but seeing this functional beauty... we completely understand, owner!

The 498cc square-four engine, with its rotary disc valves and two carburetors positioned on each side of the engine, is in its original configuration. However, it has undergone a full overhaul by KENZ, and features expansion chambers with beautiful cut-ring welding marks. Notably, the rear two cylinders' expansion chambers cross over to achieve the same length as the front ones, fitting precisely within the aforementioned seat rail with ample clearance.

The frame is also original, apart from the cut seat rail, with no additional reinforcement. However, the suspension has been completely revamped. Suzuki genuine parts that suit the XR74's appearance have been carefully selected and modified, including 43mm conventional fully adjustable forks, a curved swingarm, and 17-inch front and rear wheels with a shape reminiscent of classic Suzuki GP machines.

The painting of the fairing was handled by Alpha-Rays. This is not just a simple white and blue Suzuki color scheme; the white parts, including the wheels, are a "slightly bluish white" based on the XR45. Such historical accuracy enhances the overall completeness of the vehicle. To achieve this, they even visited the Suzuki Museum ("Suzuki History Museum") to observe the actual machine.

The engine has been fully overhauled using replica parts from overseas, and with custom expansion chambers and corresponding carburetor jetting, it produces over 100ps. The photo shows the duct removed to reveal the carburetors; an air cleaner box is installed.

A layered radiator for the 400/500 Gamma is installed. Incidentally, while genuine parts supply for older Suzuki models is quite difficult, according to Kawashima, replica parts for the square-four are becoming more readily available, particularly in the UK, making overhauls entirely feasible.

The expansion chambers for the rear two cylinders, which fit perfectly into the custom seat rail, cross just after the cylinders to ensure the same length as the front ones. The transparent hose running alongside the custom aluminum 2-stroke oil tank is for checking the oil level.

The suspension is configured with Suzuki genuine parts that evoke the XR74's atmosphere, such as the conventional front forks and Marchesini three-spoke-style wheels. The 310mm diameter brake discs were custom-made by Sunstar to match the design of the works machines of the era, a KENZ original part (¥52,000 each; also usable on 1988 GSX-R750 and 1989 GSX-R1100). The rugged Nissin calipers are also the type used on works machines of that era, and were fitted to Kawashima's own 500 Gamma TT-F1 specification machine.

The swingarm is from an RGV250 Gamma (VJ22), chosen for its curved right side, which is similar to the XR74 (even closer to the following year's XR75). However, since the rear suspension configurations of the 500 Gamma and VJ22 are completely different, the rear shock mount had to be fabricated, and the linkage lever ratio adjusted, requiring considerable effort. The rear wheel width is 4.5J, which is the maximum width that can be fitted to the VJ22 arm (the front width is 3.5J). As a side note, this pressed aluminum swingarm used on the 1990-1992 VJ22 is popular among custom bike enthusiasts, and used parts tend to be scarce and expensive.

The rear shock mount for the swingarm, fabricated to match the 500 Gamma's full-floater rear suspension, features an intricate "sandwich" construction of pressed aluminum. The rear shock is an Öhlins from another model, and the full-floater linkage side has also been modified to match the Öhlins, making the VJ22 arm conversion a complex undertaking. The expansion chambers for the front two cylinders, configured as dual right-side exits, have a connecting bracket just before the silencers to suppress vibration.

The XR74 tail cowl features heat-dissipating ducts for the three expansion chambers and silencer ends protruding from the rear, giving it a racy look. Although made of FRP, it is very light (thin-walled) as expected of a racing part. The fuel tank is from a VJ22, with the tank cap replaced by a TWM (Italy) unit. Although it looks like a quick-release, it is lockable. The license plate with the single character "Aki" hints at the owner's history.

The XR74 fairing is equipped with maintenance lids on both sides for the carburetors. While not functional on the 500 Gamma, these are important details that contribute to the "authentic feel."

The front fender is a Suzuki GP machine replica made in Finland. Such attention to detail enhances the overall quality.

The steering stem is also a Suzuki genuine part, but numerous modifications have been made, such as changing the position of the handlebar stoppers. The clip-on handlebars are mounted very low to match the fairing, and the fairing stays have been custom-made to fit the XR74 fairing.

The meters are Stack brand, capable of displaying speed and distance on the LCD. Daytona water temperature and indicator lights are stylishly installed, along with the ETC indicator in the same location.

The front turn signals are integrated into the bar ends to minimize their visual impact. The rear turn signals are vertically mounted on either side of the license plate.

The left and right footpegs are KENZ products. The custom-made bracket for the master cylinder also hints at the challenges involved in building a custom machine.

The base motorcycle was in non-running condition, so restoration work such as rewiring the electrical system was also performed. Enjoying the beautiful cut-ring welding marks on the expansion chambers is a privilege unique to two-stroke engines.

The Value Embodied in the Effort and Time Invested

The project began when the owner, residing in Akita Prefecture, brought his RG500 Gamma, which had been stored for over 20 years, to KENZ. The request was to "recreate the dream works racer using the Gamma as the ultimate machine for my retirement."

"He arrived at the shop with his Gamma on a light truck, without an appointment," Kawashima recalls with a smile. The owner had seen a KENZ-built Herve-colored 500 Gamma previously and was inspired to visit. The entire process, from that point to completion, took approximately two and a half years and cost around 5 million yen.

Some might be surprised by the cost, as expensive custom parts like racing magnesium wheels or brake calipers were not extensively used. However, as mentioned earlier, the extensive fabrication of custom parts based on historical research to achieve the XR74's atmosphere, along with repeated measurements and test fittings, and the overall effort to create a form that is "flawless to anyone's eyes," took over two years. For seasoned custom bike enthusiasts, this might even seem like a bargain.

KENZ's basic philosophy is: "If a part doesn't exist, we'll make it." This is essential for recreating the XR74's essence. While they do use replica parts from overseas or items sourced from auctions, they rarely fit without modification. They carefully discuss various options with the owner, deciding on fabrication, finishing, polishing, and painting for each individual part. These processes can incur costs equal to, or even exceeding, those of installing expensive racing parts.

Conversely, Kawashima states, "If asked to install the latest upside-down front forks on this Gamma, I would probably refuse." Having been deeply involved with the RG75 and RG500 Gamma during his time as a full-time All Japan racer, his attachment to these bikes is even greater than the owner's. In fact, the owner was reportedly speechless with emotion upon seeing the completed machine.

Incidentally, KENZ is currently building another 500 Gamma (their fifth) in the Walter Wolf livery. While appearing stock externally, its suspension and swingarm have been modernized. KENZ is open to consultations regarding custom builds of the 400/500 Gamma, starting from the vehicle acquisition stage, including specifications like these.

Of course, they also work on other models. During our visit, the shop was filled with a diverse range of machines, including a Yamaha OW01, air-cooled two-stroke RD400s, a six-cylinder Honda CBX, an early model Suzuki RG250 Gamma, and of course, KENZ's signature Hayabusa and GSX-R1000s. This broad range of expertise, from vintage to the latest models, is a hallmark of the shop.

The fifth machine features modernized suspension, with 41mm conventional forks and 17-inch front and rear wheels, composed of Suzuki genuine parts that, while different in shape, are similar to those used on the fourth machine. The stock-style gold wheels are striking. The Walter Wolf livery applied to the Clever Wolf stock-shape fairing meticulously recreates the color tones of the racing colors from that era.

Like the fourth machine, the conventional forks are 41mm in diameter, and the 17-inch front and rear wheels are composed of Suzuki genuine parts, although their shape differs. The stock-style gold wheels are tasteful.

The expansion chambers on the fifth machine are Sugaya brand, a classic choice for the square-four Gamma. Unlike the stock version that fits perfectly within the tail cowl, these protrude, which is characteristic of their style.

KENZ's shop, filled with many motorcycles from the 1980s and 90s. The number of vehicles brought from distant locations is increasing, as there are few shops capable of handling such work nearby.

 

KENZ SPORTS

Founded in 1982, KENZ is led by Kenzaburo Kawashima. Kawashima is a former editor at Yaesu Publishing's "Motorcyclist" magazine, an International A-class rider who competed in All Japan TT-F1 and Suzuka 8 Hours races on RG500 Gamma and works 500 Gamma machines. He later managed a Suzuki satellite team, winning the All Japan Championship. His extensive career gives him unparalleled expertise with Suzuki motorcycles such as the RG400/500 Gamma, GSX-R, and Hayabusa.

- Location: 31 Sasatsuka, Misato City, Saitama Prefecture
- Business Hours: 10:00 AM - 7:00 PM (until 6:00 PM on Saturdays, Sundays, and holidays)
- Closed: Every Thursday / Every other Wednesday
- Tel: 048-949-0118
- https://www.kenz-pro.com

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