Naked Gamma: Custom Suzuki RG500

Suzuki RG500 Gamma Custom

“A screaming riot of two-stroke lunacy” from ETTO Motorcycles… 

Introduced in 1985, the Suzuki RG500 Gamma was closely patterned after Suzuki’s 500cc Grand Prix bikes, which had earned four world titles and 50 GP victories since hitting the track with Barry Sheene in 1974. Most recently, the RG Γ 500 GP bike had won consecutive championships with Marco Lucchinelli in 1981 and Franco Uncini in 1982.

Many point to the square-four configuration as the secret to the RG’s success, as the centralized mass of the four cylinders created a more balanced motorcycle.

In the late 70s, you could actually buy a production version of the RG factory racer for about £12,000, do some tuning, and take it racing. Reportedly, the bike differed only little from the works version.

“In 1981 Dutchman Jack Middelburg rode his production RG to victory at the British GP at Silverstone, overcoming King Kenny Roberts’ factory Yamaha on the last lap. That was the last time a privateer machine won a premier-class GP. Imagine that now.” –MCN

Jack Middelburg on his privateer RG500

In the early 80s, the manufacturers began to release street-legal versions of their GP bikes, often known as “repli-racers.” These included the Yamaha RD500, the Honda NS400, and the mighty RG500 Gamma. The road-going Gamma was frighteningly similar to the race bike, featuring a 498cc square-four engine with four flat-slide Mikuni carbs and 95 horsepower on tap.

“The Suzuki is almost an exact replica of the race machine, its roots can be traced directly to the 1983 factory XR45 and the crankcases, barrels and general engine layout are virtually identical to the bikes ridden by Sheene, Mamola, Crosby and the rest of the factory boys.” –Classic Motorbikes

The engine had two cranks geared to a pilot shaft that went out to the wet clutch. The street version had a damper to ease the shock of so much power racing toward the transmission. However, besides lights and a license plate mount, there were few other concessions for use on public roads.

RG500 Gamma in OEM trim

The Gamma remained a track Thoroughbred at heart, packing the equivalent power of four 125cc two-stroke engines.

“In its powerband the RG500 is a vicious motorcycle that’s more at home on the track than on the road.” -Mat Oxley, MCN

Photo: Team Heron Suzuki

The bike weighed just 154 kg (340 lbs) dry — one kilo lighter than today’s $100,000 Ducati Superleggera, even with the Duc’s modern array of titanium, magnesium, and carbon fiber.

One of the greatest testaments to the Gamma’s track-bred pedigree was the time Kevin Schwantz raced a street-spec RG500 at Assen in the TT Formula 1 class.

“For TT F1 World round held at Assen, the US rider rode a virtually standard 500 Gamma literally taken out of stock at Suzuki GB and race prepped the week before.” –Classic Motorbikes

The bike had zero engine modifications. It was literally a street bike, safety-wired, with the lights removed and a set of competition tires. Schwantz finished second to Joey Dunlop on a factory Honda V4!

Recently, we heard from Ian Davis of ETTO Motorcycles, who built the Yamaha TRX 850 cafe racer we recently featured. Ian had a customer who wanted a one-off RG500 with just two requirements:

“I don’t want a fairing and it has to have riser bars.”

Suzuki RG500 Gamma

Ian, who’s both a traditional sheetmetal fabricator and suspension technician, swapped in a set of modern USD forks from a 2005 GSX-R1000 up front and a GSX-R750 swingarm with Maxton shock out back — the latter was quite the undertaking, requiring Ian to build a jig using an original RG500 swingarm. Meanwhile, the subframe was rebuilt to fit the one-off fiberglass tail section, electronics, custom oil tank, and more. 

Suzuki RG500 Gamma

This square-four streetbike is now rolling on a set of lightweight Dymag wheels with Yamaha “gold dot” calipers, as used on the R1, matched with ISR discs.

Suzuki RG500 Gamma

Ian put his fabrication prowess to good use with the bespoke oil tank, oil cooler, number board, mudguards, modified tank, and more. Meanwhile, a trick race dash keeps the rider abreast of engine RPM, speed, and more.

Suzuki RG500 Gamma

As for the engine and pipes, they’re the work of two of the most well-respected names in UK two-stroke tuning, John Floyd (Floydy Racing) and Mark Dent (Performance Fabrications).

Suzuki RG500 Gamma

The square-four was blueprinted and tuned by Floydy Racing, while Performance Fabrications built the quad chambers. Horsepower is now estimated to be north of 100 bhp.

Suzuki RG500 Gamma

As you might imagine, the 100+hp tuned square-four two-stroke engine, upgraded suspension, lightweight wheels combine to make one monster of a street bike. Says Ian:

“The bike will be a screaming riot of two stroke lunacy out on the road.”

Sounds like our kind of machine! Below, we talk to Ian for more details and the full build sheet on the project.

RG500 Gamma Custom: In the Builder’s Words…

Suzuki RG500 Gamma

I built this bespoke Suzuki RG500 for a customer. His only stipulation was, “I don’t want a fairing and it has to have riser bars.”

So this is what I built. The colours are inspired by Team Heron Suzuki and the number is Randy Mamola’s, from when he raced with Barry Sheene. It’s a heavily modified chassis, tuned engine with stunning high end parts parts.

Suzuki RG500 Gamma

I did the front and back end swaps, fabricated the custom oil cooler and number board, modified the tank. I couldn’t find a mudguard that suited the vibe, so fabricated one. And a huge list of detailing including a hidden latch for the tank.

• Can you tell us what chassis mods were done?

The frame was cut at the back and the subframe was completely altered to fit the one-off fiberglass seat unit, electrical parts, and a custom oil tank with aero filler cap, and original Suzuki oil level sender unit.

Suzuki RG500 Gamma

The head stock has a custom bracket welded on to fit, the custom speedo bracket. The frame’s airbox housing was modified to relocate a custom ally battery box. A cool neat tank release latch was made and fixed to the frame, in a hidden location (for aesthetics). The frame was further modified to accurately locate the Valter Moto rearsets.

• Was there anything done during this build that you are particularly proud of?

My favourite part was fitting the GSXR swingarm. It was extremely complicated. I had to make a jig using an original RG500 swingarm, cut the suspension lugs off, modify the GSXR swingarm, and fit all the parts on the jig and weld it up. 

Suzuki RG500 Gamma

• Can you tell us what it’s like to ride the finished bike?
The bike was delivered to the customer who loved it to bits. It has yet to be ridden, as the bike then went straight to an RG500 engine specialist for final setup and running in. With 100bhp, upgraded forks, Maxton rear shock. The lightweight Dymags and a colossal amount of weight reduction, both to sprung and unsprung mass. The bike will be a screaming riot of two stroke lunacy, out on the road.
Suzuki RG500 Gamma

Build Sheet

  • Tank modified with a double filler
  • GSXR750 K5 swingarm
  • GSXR1000 K5 forks
  • Yamaha Gold spot radial calipers
  • ISR discs
  • Dymag wheels
  • Floydy Racing blueprinted and tuned engine
  • Performance Fabrication pipes
  • ETTO Custom oil tank
  • ETTO mudguard
  • ETTO Modified frame
  • Trans Race Dash 2

Follow the Builder

Instagram: @ettomotorcycles

One Comment

  1. WHAT a bike!! I’m drooling..

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