“I always wanted a roadrace-worthy Harley with a big-Twin motor.”
If anyone but Curt Winter told me that, I’d smirk and say something like, “good luck with that.” What American sportbiker wouldn’t want the torque of a Big Twin built into the handling of a roadracer? Too bad the heft and girth of the “Big Twin”—a moniker applied to the non-Sportster Harley-Davidson engines as well as their aftermarket clones—powerplant makes packaging a motorcycle with a sporty wheelbase almost impossible, right? Wrong—and you can’t tell a man he’ll never build his dream when he’s standing right next to it.
The 45-year-old San Leandro native has always loved motorsports; his dad, Frank Winter was a mechanic, machinist, “street hooligan” and the go-to guy for tuning work in his circle of riding buddies. “My dad rode an old rigid-frame Triumph with a Panhead motor in it,” Winter said—in the Winter family, you built what you wanted. “When I was a kid, I didn’t have money, but I had time and tools and my dad. He never gave me stuff, instead he gave me tools, parts…the stuff to build it.” When Curt was 10, he took the grinder and welding torch to his Mustang minibike, converting the rigid frame to a swinger with some pieces of flatbar and the springs from the saddle. He traded in the Mustang for a Yamaha JT2, which he rode and raced as a teen. After high school Curt went to work for the family business, Mar-Len Supply—which he helps run with other family members to this day.
Sharing space in the time-worn but tidy shop is Winter’s full-time business, BTRmoto. Over the past few years, he’s fabricated frames and other parts for over 40 projects—mostly hill climbers, where his 200-horsepower, nitro-fuelled Harley-engine racers do quite well. Curt’s racing career started when he was a teenager, and now he and teammate Jamie Perry attend hillclimbs all over the country with his family in tow.
Still, he’s always loved riding pavement, but like his father, likes the authoritative thump of the Big Twin. Back in the early ’90s he built his first Big Twin streetfighter, a bike so clean and well-built it caught the eye of Battle2Win and Thunder Press founder Reg Kittrelle. Since then, he’s been doing custom projects—a notable client is Arlen Ness, with Curt’s work featured on a Discovery Channel program—mostly with a sportbike slant.
When Winter decided he wanted a competitive roadracer, he knew what he had to do. His very compact and neatly packaged streetfighter still put 59.25 inches between the axles—okay for the street, but not ideal for racetrack-level handling. “It makes a shorter swingarm, with too much pivot angle.” He put an $800 Twin Cam 88 motor—pulled from a bagger and sold on eBay—up on his bench and thought, “what’s the minimum I need?” Stripped to the basics, with the primary case and transmission it was still about four inches too long, so Curt knew what he had to do—build his own transmission case.
High-end builders like Ecosse and Confederate have built such units, but they don’t sell them to working stiffs unless we buy an entire motorcycle—big bucks. But Curt’s been building his own stuff all his life, so “I took a gearset, blocked it up behind the motor and then built a case to keep it there…I don’t have any CAD stuff or CNC, it’s all manual. Super-basic.” Sounds easy, right?
And it works. I wasn’t able to ride the bike on a racetrack and instead just got a quick spin on the lightly trafficked roads near Curt’s Hayward shop. The bike is small and light—Curt says 405 pounds with a gallon of gas in the hand-formed aluminum gas tank (“I only make them for myself, says Curt”)—and the wheelbase is 55.25 inches, two inches shorter than he could build with a Sportster motor. The front end is late-model GSX-R1000, with the attendant bad-ass brakes. Carbon-fiber wheels shaved 25 pounds. The bike is easy to ride, even with tall gearing, thanks to the unbelievable torque the bone-stock (aside from carb and exhaust) Twin Cam 88 motor makes—115 foot-pounds, seemingly right off idle.
Curt rubber-mounted the big mill, but vibration is noticeable, contrasting with the crisp, modern feel of the chassis. It’s rough and vintage feeling, but Oh My God does it pull hard in the midrange. Put him on a technical course like Sonoma Raceway and Curt (who just recently had his first trackday) says he gobbles up B-group riders on Ducati Panigales and Japanese superbikes like potato chips.
The chassis is remarkable. The GSX-R suspension is compliant, not harsh, and the Ducati 999 shock and linkage do a good job in back. Curt’s hill climbers make more than 200 hp, so he knows how to build a frame to handle big numbers, and the giant aluminum swingarm (also built by Curt) should be icing on the rigidity cake. The brakes are four-piston radial-mount calipers and massive soup-plate floating rotors. They’re fine, believe me.
My only concern with this motor would be vibration, though Curt does say the vibes lessen at higher rpm. Even at low speeds, the buzz and rumble from the V-Twin made my eyeballs jiggle and blur my vision, but Curt says it can be tuned out (at least partially) with blueprinting and other touches In the Big Twin world, stock is just the starting point.
Curt wants to keep developing the BTR GP, as it has plenty of potential. He says he can save more weight with a trellis-style steel swingarm and going to a magneto ignition, which would save 15 pounds and add some power, thanks to reduced drag on the crank. But it wouldn’t stop there—an array of hot rod Big Twin clones will fit in his frame, including the fearsome Ultima T-VO, a 127 cubic-inch monster that “out of the box” makes 140 hp and 145 ft.-lbs. of torque (covered with a three-year warranty). And then you add the turbocharger, which could net over 200 hp. Suddenly, the bike goes from a quaint (but good-handling) VW Microbus to a McLaren supercar. Needless to say, several enthusiastic roadracers—retired champ Michael Ernest and Pacific Track Time’s Ken Kesey among them—want to help develop the bike and make it a contender.
An air-cooled, long-stroke pushrod motor may create questions about reliability, but Curt has that handled. His bike has an upgraded oil pump—a common weak point—and he’s not worried about the press-fit crank twisting under extreme loads, as roadracing doesn’t create the stresses a drag bike or hill climber might experience. Another moto-journalist rode the bike all day at a track day, bouncing the poor thing off the rev limiter until it started leaking oil, but there’s no reason to ride the bike that way; power drops off well before redline. One thing building your own bike teaches you is to respect machinery.
But what’s this all about, really? Curt says he would like to use it to showcase his transmission design and ultimately develop a production Big Twin sport-tourer (he’s already built bikes like that for clients). It’s also a rolling business card for a talented fabricator and race bike builder, but even though Curt admits that now, with a busy family and professional life it’s easier to just buy the things he wants rather than make them, sometimes there’s stuff you just can’t buy. “I’ve always wanted a track-worthy Harley and this is the best.”
Gabe Ets-Hokin is the Editor of City Bike magazine, and a frequent freelance contributor to MotorcycleDaily.com