Bimota HB1 Tribute
Engine: 736cc air-cooled OHC inline 4-cylinder, 61mm x 63mm bore and stroke, 9.2:1 compression ratio, 58hp @ 8,000rpm
Top speed: 115mph (est.)
Carburetion: Four Keihin 28mm
Transmission: 5-speed, chain final drive
Electrics: 12v, Dynatek electronic ignition
Frame/wheelbase: Perimeter-type chromoly tube frame w/engine as stressed member/57in (1,448mm)
Suspension: Replica Ceriani tunable telescopic forks front, dual Marzocchi shocks w/adjustable preload rear
Brakes: Dual 11.6in (295mm) discs front, single 11.6in (295mm) rear with Brembo calipers
Tires: 110/80 x 18in front, 130/80 x 18in rear
Weight (dry): 440lb (200kg) (approx.)
Seat height: 30in (762mm)
Fuel capacity: 4gal (15ltr)
It’s a little-known fact that Bimota started out building air conditioning equipment, which is all about keeping things cool. And while there’s no evidence Steve McQueen, the king of cool, ever owned a Bimota, the two are loosely connected through Rob Phillips of Staatsburg, New York.
The first link is that Rob sympathetically restored and owned for 10 years the first of three 1970 Husqvarna 400 Cross offroad machines that McQueen bought back in the day. The second link is that Rob produced the subtly updated Bimota HB1 replica featured here.
The Bimota name was created using the first two initials of the surnames of its three founding partners: Valerio Bianchi, Giuseppe Morri and Massimo Tamburini. Of the three, Tamburini played the largest role in designing what could be considered some of the most exotic Italian motorcycles ever produced.
Tamburini’s fascination with motorcycles began as a youngster in his hometown of Rimini, Italy. Often driving his mother to distraction, he listened for the sound of approaching motorcycles and then rushed out of the house to see them flash by.
Born in 1943, Tamburini’s career plan was to become an engineer. The family didn’t have sufficient funds to send him to university, however, so Tamburini went to trade school, where he studied cooling systems. Bimota was created in 1966 as an air conditioning company, but Tamburini never lost his interest in powered two-wheelers. He rode and tuned his personal Moto Guzzi, and he was an avid race fan, watching from the stands as well as competing on the track.
When Honda launched the 4-cylinder CB750 in 1969, Tamburini took notice. He was soon riding one, but promptly wrecked it, breaking three ribs. It’s not clear if he blamed the design of Honda’s frame for his crash, but while convalescing Tamburini drew up a replacement chassis to house the CB750 engine. Working out of the Bimota shop alongside the air conditioning equipment, Tamburini cut and welded the frame together to create the HB1 — H for Honda, B for Bimota and 1 to symbolize the first.
Sensing they were on to something, in 1972 the company was renamed Bimota Meccanica and began producing frames sold in kit form to house Japanese engines from the Big Four (Honda, Kawasaki, Suzuki and Yamaha). Bimota eventually began constructing complete motorcycles, and over the years the company has slotted engines from the likes of BMW and Ducati into their specialized frames.
Tamburini left Bimota in the early 1980s, however, when he began working with Ducati, where his name is attached to various Ducatis including the 916. He then moved to MV Agusta, where he designed the 750cc F4. Tamburini died in April 2014 at the age of 70. Bimota is still in business, still creating exotic sport bikes, and still using BMW and Ducati powerplants.
It’s the origins of Bimota, though, that caught the attention of Rob Phillips. With only 10 HB1s ever produced, their rarity got Rob thinking he might be able to corner a niche market by constructing complete HB1 replica motorcycles.
Rob runs Husky Restorations. After riding Husqvarna dirt bikes for decades, in 2006 he began collecting and then restoring the offroad motorcycles. When someone offered him top price for one of his first restorations, he realized he might be able to make some money turning the hobby into a business.
In 2008, he came across a seller in California offering a 1970 Husqvarna 400 Cross. Working from his home in upstate New York, he bought the bike sight unseen. Thinking it would simply be another Husqvarna in his inventory, he stored it in his daughter’s San Diego, California, garage. It wasn’t until he teamed up with Don Ince that he discovered just what he had. Ince held all of the documents of Edison Dye, the man responsible for importing Husqvarnas into the United States in the late 1960s and early 1970s and often called the father of American motocross.
Ince’s paperwork proved the Husqvarna that Rob had bought was one of three 400 Cross offroad motorcycles purchased by Steve McQueen in the early 1970s.
Moving beyond Husqvarnas, Rob took up another challenge when he began constructing tribute Yamaha HL500 dirt bikes. Using Yamaha TT500 4-stroke engines in specially made lightweight frames with aluminum swingarms, Rob’s builds pay homage to the HL500’s mid-1970s creators, Torsten Hallman and Sten Lundin (the HL in the name).
“I collaborate with other people on these builds,” Rob says. “I’ve got the right people doing the right things.” He used much of the same team to help create the HB1 replica, with the exception of the supplier of the gas tank, front fender and seat. While surfing the Internet, Rob found a Serbian carbon fiber fabricator who had an original tank and seat for a KB1, which is a Kawasaki-powered Bimota.
“I contacted him and asked if he could build a mold to make a set of carbon fiber panels for the HB1 version of the Bimota,” Rob says. “The Honda has a slightly different shape at the front of the tank, and he said he could alter the mold to make it work. The HB1 is a rare bike, of course, but once you have a tank and seat you’ve solved half the problem.”
Because the Bimota’s top frame rails follow the bottom contours of the tank and seat, Rob says it wasn’t difficult to establish the correct layout of the upper portion of a replica frame. He also scrutinized high-resolution digital images, analyzing them by enlarging and scaling them up for display on a wall. As the frame uses the Honda CB750 engine as a stressed member, all of the mounting points were also known. “From that, it was a bit like connecting the dots,” Rob says.
Helping to connect those dots were the people responsible for cutting and welding the tubing together, father and son team Randy and Karsten Illg of Framecrafters in Union, Illinois. While Rob makes it sound simple, there were some unique features that added to the excitement of the build, including reverse engineering the eccentric adjusters where the rear swingarm mounts to the frame. In use, the eccentrics compensate for chain wear. Rob wrote the code and used his CNC machine to accurately replicate those pieces.
With fabrication work ongoing, Rob was accumulating the Honda CB750 parts he’d incorporate on the finished Bimota replica, including hubs, headlight, hand controls and engine. A 1975 CB750 engine was taken completely apart and rebuilt by Jim Covell of Pleasant Valley, New York. Fresh bearings and seals were installed, along with a mild Megacycle cam to sharpen up performance. Stock 28mm Keihin carburetors breathe through K&N filters, with a Dynatek electronic ignition providing reliable sparking. Rob performed all the engine detailing chores.
Anchoring the front end is a set of Ceriani GP35R racing forks mounted in a custom adjustable offset triple tree that can extend or shorten the wheelbase by 5mm. With his CNC machine, Rob carved the upper and lower trees from billet 6061 aluminum. A pair of Marzocchi shocks supports the rear.
For braking duty, Rob opted for Brembo P108 calipers squeezing stock Honda rotors drilled with a special pattern. Buchanan’s Spoke & Rim supplied stainless spokes to lace the CB750 hubs into shouldered Excel alloy rims. The bike wears Bridgestone BT45 tires.
Another Honda part is the modified tachometer wearing a replica Bimota HB1 faceplate. The tach and more instrumentation, including a Dakota Digital speedometer, are mounted in a custom dash. “The speedometer is discreet, because I wanted to keep it looking like a race bike,” Rob says.
More custom parts include the aluminum oil tank handcrafted by Ian Halcott of Twinline Motorcycles in California. It’s not quite the same as an original HB1 tank, as Rob says that reproducing it exactly as original would have been difficult. Rob plumbed in the tank with one-off oil line adaptors and installed a pressure gauge, making it easier to monitor the engine’s health.
Manufacturing the exhaust proved to be one of the most tedious tasks. According to Rob, mandrel bending the headers was the easy part. “The silencers, however, are S-shaped,” he says, adding, “It took a long time to find someone who could reproduce those Magni-style mufflers. I worked with a fellow in Japan, and he handmade the ones on this bike.”
With the exhaust mounted on custom hangers, it became apparent the sidestand would not work mounted as per usual on the left-hand side of the motorcycle. Rob made a controversial decision to relocate the stand to the right side of the frame. “I’ve gotten beat up for my kickstand, but that was the best place to put it,” he says.
Rob didn’t make everything. Aftermarket parts include Tommaselli clip-ons and Tarozzi rearsets, adding some true Italian flair to the Bimota reproduction. The electronics are housed in an aluminum tray under the seat, including a modern Motogadget power distribution module. Rob also made an aluminum cover for the Honda’s starter.
Mike Carter of Oklahoma City, Oklahoma, painted the frame red, and when Rob initially assembled the HB1 — with the painted frame but unpainted carbon fiber body panels — he faced a dilemma. “I really didn’t want to paint over the carbon fiber, it looked so good,” he says. In the end he decided to complete the replica as planned, sending the carbon fiber parts to Mike for a custom HB1 paint job. Red suede covers the saddle foam.
Finished in September 2016, Rob has two years of labor invested in putting together his HB1 replica. With that kind of effort, is the resulting creation exciting to ride? “It’s a lot of fun,” Rob explains. “It’s very comfortable because your knees tuck into the tank contours. Overall, the bike is nicely balanced and it’s lighter than a Honda CB750. The carbon fiber tank itself probably only weighs about one and a half pounds, compared to the heavy steel Honda tank.
“I’ve only got about 15 miles on it, though, because I don’t actually ride much on the street. I’m a dirt bike guy at heart, but I love building them.” That’s cool, because that passion is what motorcycles are all about, whether they were once owned by Steve McQueen or, in the case of the Bimota HB1, first built by an air conditioning company. MC
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