Ultimate Street-Legal Sportbike: Stage 1
The plan was simple: Make a full-on, race-ready Heavyweight Superbike, but make it docile enough to be an everyday street bike. Okay, maybe not so simple. Typically a race bike is finicky, idles high, runs hot when not at speed, etc.; not very conducive to street use. But what sportbike, street or trackday rider doesn’t dream of owning a superbike that can be ridden to the coffee shop every Sunday? That’s just plain cool. So, we did it anyway! Well, Grant Matsushima at MPT Racing did it for us. In our recent do-it-all sportbike shootout the Suzuki GSX-R750 came out on top by virtue of its incredible all-around capabilities both on the street and racetrack. But we all would have liked some additional
power. This is where Matsushima first came into the equation. Originally consulted to build a “street-able superbike engine,” he quickly jumped at the task of building the entire motorcycle, leaving us to simply gather the parts needed. Thanks, Grant!
Engine-wise, Matsushima went to town on the 749cc powerplant, changing out to ’07 GSX-R cams and decking the head; plus a host of other black-magic engine-builder secret stuff, with the end result being horsepower numbers well above 150 at the rear wheel. Exhaust gasses are now spent via a one-off, handmade MPT system that features an interchangeable muffler design. Option One, the MotoGP option: Straight, slash-cut end pipe, and while extremely loud, it sounds amazing – straight up GP bike for the street. Option two: Simply remove one clamp and bolt up a KR Tuned muffler, which takes it back down to normal street-legal sounds, even featuring a quiet-baffle insert to bring it to nearly stock dB levels. All this from a reliable, street-able motorcycle!
Brembo monobloc calipers and radial master cylinder make for some of the best brakes we have ever tested.
As for the bolt-on parts, for Stage One a full set of Brembo Superbike-spec brakes were mounted, featuring uber-trick monobloc front calipers mated to a radial master cylinder, adjustable between 18mm and 20mm piston sizes for tunable feel and feedback. We used Kevlar-coated steel-braided brake lines. Suspension is handled via full Ohlins
cartridge drop-in fork internals up front, while out back sits an Ohlins TTX shock.
Vortex rear-sets make for a fully adjustable, easy-to-change riding position, so as to accommodate both street and track use. Vortex also threw in a trick shorty clutch lever, as well as shorter gearing making for additional acceleration at the twist of the wrist. Grant eliminates one of the throttle cables for the same purpose. GPR’s V4 stabilizer keeps the front wheel in line over the bumpy stuff, while Dunlop 209 GP “A” rubber front and back glues her to the pavement.
Rounding out Stage One was a fully custom look by owner/artist Matt Polosky of Color Zone Designs, a Huntington Beach-based do-it-all paint shop. We went for a Barry Sheene retro-meets-new look, modeled after the Suzuki GP bike Chris Vermeulen rode at Phillip Island last year, complete with Vermeulen’s old number 71 on the side. Quality of the
paint work is top notch, as was the turnaround time.
For the maiden voyage we took her out to Laguna Seca recently for a Track Crafters trackday and performance was incredible. Handling was on par with that of any supersport bike I have raced, plus an engine that could run with every 1000cc machine I encountered all day, and off-the-charts, onefinger brakes. Truly amazing considering I then used
the bike in its exact same state to commute to and from work the following week. An incredible combination, no doubt.
Stay tuned for Stage Two. We’ll be adding lightweight wheels, traction control and a host of other parts to really take this GSX-R to the max!