A Bonneville For Bonneville

Riding South Bay Triumph's Record-Setting Turbo Twin

By Alan Cathcart, Photography by Andrew Cathcart, Phil Hawkins, Steve Bohn

Triumph motorcycles have a long and distinguished history at Utah's Bonneville Salt Flats. In fact, its most iconic model is named the Bonneville, in honor of an outright motorcycle speed record set by Texan Johnny Allen in his Triumph streamliner in 1955. Matt Capri has a colorful history on the salt as well. The founder of BMW tuning house Luftmeister, Capri set his first speed records at Bonneville in the '80s, riding various normally aspirated and turbocharged BMWs. He opened his South Bay Triumph dealership in '95 and began setting records with the British brand shortly thereafter, including one in excess of 200 mph on a turbocharged Daytona.

With such a proven track record building performance bikes, and such a close relationship with Triumph, it was only a matter of time before Capri turned his tuning talents to the new-generation Bonneville. And, given his history of record-breaking turbo bikes, it was inevitable he would build a turbo Bonneville. Two years ago he finally did, after a few years spent collecting parts for the special project. "I tried to get support to do this earlier, but we couldn't get any help," Capri says. "No one thought you could make a twin boost, so I decided to do it myself."

Capri's first attempt debuted at Bonneville in August '08. It was entered in the 1000 PB-G class (1000cc Production Blown Gasoline), with Capri in the saddle. He only completed two passes that year, but went fast enough to establish a new AMA national class record of 161.288 mph. The bike actually went 168 mph on the first run, but the two-way average suffered when Capri's loose-fitting leathers got sucked into the turbo intake on the return run, reducing boost. Capri then handed the bike over to a lighter, more aerodynamic rider in an attempt to raise the record. That effort ended badly after the hired jockey held the engine against its rev limiter too long and cracked the cylinder head.

Capri might have failed to find the bike's ultimate top speed, but he did satisfy another objective by setting a record at Bonneville aboard a Triumph Bonneville on the eve of that model's 50th anniversary. He also honored the late, great Bonneville legend Don Vesco's rule: "You shall not leave the salt flats until you have broken all of your parts." Mission accomplished, then.

In actuality, Capri was just getting started. He returned to his shop with the goal of coaxing more power and greater reliability from the turbo Bonneville. Capri identified a special opportunity in '09, following the FIM's radical overhaul of its world speed record categories. Previously, categories were defined by engine displacement only. Number of cylinders was irrelevant and, as a result, nearly every record from 750-2000cc was the property of a four-cylinder Suzuki. New rules, however, would take the number of cylinders into account. This revitalized the sport, and delivered countless new record opportunities to Capri and others competing with European and American twins.

Capri zeroed in on the FIM world record for 1000cc Twin Cylinder Blown Unstreamlined motorcycles. With an added year's worth of development on the Mickey Cohen Motorsports dyno, the turbo Bonneville was now producing 230 horsepower at the rear wheel. Since yours truly already had an FIM international competition license, Capri asked me to ride the bike, while he led a support crew including Roger Russell and my son Andrew.

My first challenge was learning to ride the bike, which wasn't easy. The riding position is radically different from a stock Bonneville, with a low, cut-down fuel tank and the seat swept up at the back to make room for the turbo behind the engine. The footpegs were relocated a good distance rearward to create a more aerodynamic riding position, which forces you to change gears with your left toe pointed at the ground. There's no front brake, but no rear brake pedal either-squeezing the lever works the rear stopper. The hopelessly inaccurate stock Triumph tach was blanked off, so I shifted according to the boost gauge and the 9300-rpm rev limiter.

Capri set the turbo to produce a serious 17 psi of boost and it came on very suddenly, hitting the rev limiter very quickly. The awkward shifter made grabbing the next gear difficult, but I eventually sorted it out. My first pass was a modest 155 mph-not especially impressive considering I had earlier gone 153 mph on Capri's naturally aspirated Triumph Thruxton, establishing two new FIM world records in the process. My return run, however, was significantly more promising: 171.624 mph. That's more like it!

This turned out to be as close as we got all week to a speed that was representative of the bike's true potential. I was eventually able to set a new FIM world speed record for the flying mile at 165.405 mph-and 165.672 mph for the flying kilometer-but trying to improve that mark only resulted in breakdowns. First the throttle bodies were blown clear off their intake stubs, unable to withstand so much boost! Safety-wiring these on resumed normal service, but on the next pass the shift linkage disintegrated, forcing me to abort that run, too.

This could have been interpreted as another message from Don Vesco's ghost, but Capri wanted to make at least one pass at over 180 mph. With just 35 minutes remaining before the 2 p.m. shutdown, we staged again. Just as the starter waved me onto the course, Andrew rushed out and stopped me. He'd spotted the foil-wrapped fuel lines leaking. And so it was for another year.

With sore heads from an impromptu celebration of the Bonneville's 50th birthday the night before, the South Bay Triumph team left the salt flats already planning for this summer's return attempt. "For sure the Turbo is a 180-mph motorcycle," says Capri. We just need Vesco's ghost on our side this time.

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