Sports bike engine for custom hardtail

Sporting the number plate GOFAT, this jaw-dropping creation combines the aesthetic qualities of a classic hardtail cruiser with the modern-day powertrain technology of a top-shelf super bike.

It's difficult to fathom why an owner would want to take the engine, gearbox and front end suspension of a 2005 Yamaha R1 sports bike and then build a retro bike around it with no rear suspension, but that's exactly what Todd Treffert tasked American custom shop Speedconcepts with.

The Wisconsin-based outfit created what is lovingly referred to as 'Fatty' (the name discreetly inked on the fuel tank) and though there is no rear suspension to absorb ructions in the road, there is a hidden suspension system for seat, providing rudimentary spinal support.

Design wise, the buyer wanted something inspired by early race bikes from the '20s and café racers from the '60s, according to Speedconcepts.

Though no output is given for the paired-back hardtail custom, the stock standard 2005 Yamaha YZF-R1 developed a very handy 134hp (100kW), and when combined with a couple of exhaust tweaks and the addition of a Power Commander, the Fatty could be good for up to 150hp.

The frame is a custom hardtail job, with an impressively swoopy design, and features a fibreglass buttress around the custom radiator that adds a little more character to the Japanese-engined motorcycle, while also protecting the cooling system.

Other notable design features include the tank and a large 23-inch front wheel which is hooked up to the Yamaha R1's front suspension and brakes. The rear wheel is a 20-inch hoop and the front and rear are shod with 130 and 280 aspect Avon tyres respectively, while Rizoma rearsets were installed.

The front race number plate is a fiberglass unit that "hides the instrument cluster and presents the headlights perfectly," says Speedconcepts. "The idea for paint was to keep it simple, so the frame was painted a gloss black while most of the other items were painted a flat black. To keep it race inspired, flat black numbers were added in a flat ivory background."

Even the R1's wiring harness and instrumentation has been retained, but the exhaust system is vastly different. Covered with heat tape, the quad exhaust pipes exit above and below the seat respectively, and judging by their straightforward design can be expected to deliver a very loud sound track.

Check out Speedconceptsonline.com for more details on the custom shop.

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