The bike is supposed to be good for 149 MPH stock. That's if you have a space long-enough to let it run, you aren't 6 ft 4 inches, 240 lbs, and you're not at 6,000 ft above sea level. Bikes commonly have about 110 RWHP, the highest I recall seeing in a USA bike magazine test was 119 RWHP.
A Gen II is supposed to be capable of something over 170 RWHP which is better-than a stock Hyabusa, but the Hyabusa hits its 300 KPH from aerodynamics. Power adders on either one can make a lot-more HP. I am not a professional mechanic. My friend's shop works on a lot of Hyabusas they've built with big HP #'s. As you suggested, the 300 KPH speed is suspect. It sounds more-like a 'bench-racing' tall-tale.
Going back many years,
Sport Rider magazine in the 1990's, invited a bunch of tuners/shops to run their bikes. The bikes had to be street-legal, they had-to be ridden on the street, and the competition was at a strip and at a top-speed location. This was before the Suzuki Hyabusa was released.
A guy I know from south Florida, Mark Moisan, brought his Suzuki GSXR 1100 to the event. Its main power-adder was turbocharging. He did OK in the dragstrip event, but a short wheelbase bike with a lot of power is gonna be difficult to launch so his times were middle of the pack. Where he really shined was at the venue where they did the top speed runs. His bike did 229 MPH through the speed trap and would have done better, if the cabueretors hadn't blown-off the manifolds. The bike eventually dynoed at something like 365 RWHP though at this competition I think it turned just-over 300 RWHP. Mark Moisan's wife used to ride his record-setter to local Ft. Lauderdale 'bike nights' just to-show that it was a street-capable bike. The boost was turned-down.
One of the Hyabusas from my friend's shop has turned 200+ RWHP
above Moisan's
Sport Rider dyno run.
Here is one of the bikes from my friend's shop, a '06 Hyabusa, its power-adder is NOS. It has an MTC Gen II lock-up clutch, an air-shifter, an extended wheelbase of 70 inches, and it's turned an 8.59 e.t. at 156 MPH on the engine alone.
They recently sold a Hyabusa 1363 CC with a 62 inch wheelbase, a large turbo, it turned a 7.38 at 199 MPH, and it's licensed for the street! Obviously, a street-tune is less-than a strip session tune. Their strip they usually run-at is West Palm Beach FL.
The shop built another bike, a 'sleeper' of-sorts, a 2001 GSXR 1100 frame, modified to accept a Suzuki Hyabusa engine which was bored (+5mm) and stroked (+5mm), ported, upped compression, an air shifter, and a 14 inches-over swingarm, done in-house, or with a local fabricator. Did I mention, 'NOS?' They use primarily one machinist, who has his own business, whom I've known since he was a teenager. He used to-be a machinist for Crane Cams, when it was in south Florida, his father was also a machinist there.
Not what I “did”, what I “am doing”...
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