Supercharged Superbike
Following the unfortunate demise of Buell in October, sportbike aficionados probably thought that the death knell of the American superbike had finally tolled (excluding maybe the Fischer MRX 650 which is more of a middleweight). The U.S. does have several manufacturers of V-twin sport machines-quality manufacturers like Ecosse and Confederate spring to mind-however those particular motorcycles are upright and unfaired, and brilliantly engineered though they are, arguably do not quite fit the genre.
In addition to a full fairing and track-day ergonomics, if your requirements also include Harley-Davidson based power, then the pickings now come down to just one company that fits the bill.
Walter Roehrich is a former Porsche/Audi/VW Master Technician and engineer based in Gurnee, Illinois. His first V-Rod motored superbike, the Roehr 1130 prototype, was constructed in 2004. “I went to my local dealer and realized the V-Rod engine might be a viable option,” Roehrich said. “It’s actually shorter than a Ducati V-twin, so I was optimistic I could make it work, but the main issue is its weight. I ended up buying a used V-Rod motor anyway, and things went from there.”
That first 1130 handled well enough, which was encouraging, but with only around 120 rear-wheel horsepower, the machine lacked the necessary minerals to wear the superbike moniker. Roehrich’s solution was to add forced induction, and he preferred the more consistent thrust provided by supercharging. Sprintex in Australia already had a V-Rod supercharger kit, and they were prepared to help develop it for him. However, Roehrich felt the double-rotor Sprintex unit would be too large and heavy.
Roehrich’s choice of the Danish-made Rotrex centrifugal supercharger that weighs a mere 6.4 pounds, and is little bigger than the battery, appears to have been a smart one. Rotrex’s patented roller-drive system multiplies up the compressor by an impressive 13:1 ratio, giving serious boost in the most compact package possible. The supercharger is also cleverly matched to the bike’s road speed, ensuring liquid-smooth power without the hit you normally get from forced-induction engines.
The Roehr 1250sc now claims to put out a healthy 180 horsepower at 9100 rpm, and 115 ft/lbs of torque at 7600 rpm. The motor produces the normal minimal V-Rod vibration, and aboard the 1250sc I felt immediately comfortable. The throttle has a longer twist than usual, another legacy from the V-Rod. “Actually, the first few riders complained it was a little too quick-action,” Roehrich explains, “so I lengthened it slightly; for a customer it’s easy to adjust to their preference.”
The 1250sc feels familiar and the light controls make it very easy to ride. I would never have guessed it was supercharged, judging by a power output that is so smooth and controllable. Compared to the typical Japanese liter-bike, the 1250sc feels a little unconventional simply because of its low-revving engine.
However, the motor really wakes up around 2800 rpm and serious power is available from 4000 rpm to the rev-limiter. I could hear the supercharger whining as it spun up, and that certainly adds to the excitement, but the power-although substantial-is very manageable and builds strongly until the rev-limiter abruptly cuts in.
The 1250sc retains the stock five-speed transmission, but the engine produces so much torque I found myself using the sweet-shifting transmission’s fourth and fifth gears almost exclusively. Interestingly, the V-Rod motor already comes with an efficient slipper clutch, so coupled with Brembo’s ubiquitous radial Monobloc brakes, slowing the machine is effortless and has plenty of feel.
What appears to be the fuel tank is just a cover; four bolts quickly remove it, revealing the compact supercharger system and belt drive atop the motor. Although it sits fairly high, Roehrich has done a commendable job of centralizing the machine’s mass, and the bike turns well.
The real gas tank is under and behind the seat. The chrome filler on the tail section is easily accessible-somewhat fortuitous, as a range of less than 70 miles meant I constantly had to think about filling up. Roehrich was aware of the shortcoming on this pre-production model and has now changed the fuel pick-up placement for a 100-plus mile range on the production bikes.
The Roehr’s claimed dry weight of 432 pounds seems like a bit of wishful thinking, given that a V-Rod motor alone weighs in at about 200 pounds. I certainly felt the heft maneuvering in the driveway, and the tightly limited steering lock does not help either. Once underway, the weight disappears and, with a marginally shorter wheelbase than a Ducati 1198, the bike handles superbly. For our test, Roehrich had just fitted heavier fork springs to the 43mm Öhlins R&T forks, and the front suspension was just right for the street.
Roehrich’s hybrid chassis comprises two main spars of large-section, thin-walled steel, bolted and bonded to CNC-machined billet-aluminum plates. The design combines both rigidity and feel. “I didn’t want the blower’s belt sticking out, so I had to widen the frame by two inches,” he says. The steel single-sided swingarm is claimed to weigh the same as Ducati’s cast aluminum unit, and it works a fully adjustable Öhlins shock via a rising-rate link.
The sleek, carbon fiber fairing that wraps around the twin side-mounted radiators is composited in-house, and the stacked headlights give the bike a slightly European exotica look. The two-tone paint is appealing, and the forged aluminum Marchesini wheels with Pirelli Diablo Corsas, Akrapovič carbon muffler, top-shelf Öhlins suspension and Brembo radial brakes all add to the feeling of high quality that exudes from the machine.
The balanced ergonomics and wide, single seat couple with the light-touch controls to make for a comfortable ride, and Harley’s reliable standard electrics are used. Roehr is about to replace the incongruous looking V-Rod instrument binnacle with a digital panel-no bad thing as the current H-D tachometer is a little vague and not particularly easy to read.
Walter Roehrich explains, “I’m particularly interested in machines that make life more fun and enjoyable,” and his very credible superbike has few quirks, and a hand-built, bespoke quality feel to it. It is fast as heck, handles impeccably and rides intuitively, if a little unconventionally. It is unlikely to be a successful racing machine, but it will certainly acquit itself well at any track-day. If you are looking for an American superbike that is a little different-yet, one that you will actually enjoy riding-then the Roehr 1250sc will suit you perfectly.
Photography by Don Williams
