South Bay Triumph Street Tracker motorcycle test

Menus

• Supercharged Bonnie
• Modified Triumph twin-cylinder 988 cc, 106 hp, 159 kg dry
• Discovery
• In the saddle
• In the city
• On roads
• Cycle part
• Braking
• Conclusion

Supercharged Bonnie

Modified Triumph twin-cylinder 988 cc, 106 hp, 159 kg dry

No other motorcycle has been the source of so many variations over the years as the Triumph twin, since the invention of the Cafe Racer concept during the Swinging ’60s via Dresda, Metisse and other British motorcycle tuners, victories at the Daytona 200, the 24 hours of Montjuic and on the TT races, to the crowd of Californian hotrod creations of the 60s and 70s both for road and off track, especially for flat track races at the hands men like Gary Nixon, Dick Hammer and Skip Van Leeuwen. Triumph’s parallel twin proved to be more versatile than any classic-era motorcycle and made a comeback in 2000, 10 years after the historic brand was relaunched by John Bloor. Today, the Bonneville remains the best-selling model by Triumph with more than 180,000 units produced since the relaunch in 2000..

And although Triumph itself delivered a sportier version of its Bonneville in the form of the current Thruxton 1200 R, it is curious that so few tuners in the world today attach importance to the ‘improved performance of those air-oil cooled 8-valve DOHC engines which replaced the original OVHs. This is what made South Bay Triumph’s Matt Capri stand out, and not just his Long Beach, California dealership. He was the best Triumph distributor in the United States. For decades, Capri’s Mod Catalog offered Triumph owners a wide range of parts to improve the performance of their twin-cylinder models. Now withdrawn from sale, Capri continues to create bespoke Triumphs for a handful of customers relying on the Bonneville engine of which he has become an expert..

South Bay Triumph Street Tracker test

Discovery

A native of New York, Capri moved to California in 1973 to become the West Coast Sales Manager for BMW. He built the R90S Superbike with which Steve McLaughlin first won Daytona in 1976. Then he founded in 1980 Luftmeister, the BMW preparation department which during the following 15 years would set numerous speed records with boxers turbocharged by Capri and standard, just like K series 4 cylinders. In creating South Bay Triumph in 1995, Matt joined the British brand at the start of the Bloor era and was one of those to bring the brand back to the United States. . I am proud to say that it is thanks to Matt’s skills that I am currently the holder of several FIM World Speed ​​Records on the South Bay Triumph Bonneville in the 1000cc twin cylinder standard and forced intake categories..

Speed ​​record at Bonneville on the Triumph prepared by Capri

One of his clients duly ordered a complete Street Tracker, built around a racing Flat Track frame that Capri ordered and powered by a Bonneville engine tuned to the same performance level as used on my World Record Thruxton, all completed by a somewhat flamboyant paintwork done by Bob Cunningham’s workshop in San Pedro with a frame repainted in the same orange as that of a Dodge Charger. This bike could only come from Southern California and I had the opportunity to try it out before it was delivered to its owner (thanks to him too).

The South Bay Triumph Street Tracker

The Street Tracker’s lightweight twin-shock frame weighs just 14.5kg with the swingarm and is identical to the one used by the West Coast Triumph AFT, the American Flat Track racing team for which Capri is riding. occupies engines. This 4130 CrMo steel tube open cradle frame uses the Bonneville’s heavy engine (weighing approximately 100 kg) as a load bearing element, which allows the Tracker to weigh only 159 kg with the oil, but no fuel in it. 10.2 liter aluminum tank.

The frame is derived from the flat track proto

Big weight savings have been made thanks to the Carrozzeria forged aluminum rims which alone are 9 kilos lighter than the original pair fitted to the Bonneville. The 18-inch front wheel is associated with a single 310 mm Galfer disc clamped by a Beringer Aerotec radial caliper attached to a 41 mm KYB fork taken from a 2004 Yamaha R6. The geometry displays a caster angle of 26, 5 ° and a 97 mm drag, the fork is adjustable in preload and rebound, while only the preload is adjustable on the two Ohlins shocks, located on either side of the 17 "Carrozzeria wheel carrying an EBC disc of 254mm and a Brembo two-piston caliper.

Street Tracker’s Цhlins shocks

Beyond the flashy paint, another pure product of the California custom scene is the quilted saddle, hand-sewn with orange stitching referring to the frame. The curved handlebars and the adjustable brake and clutch levers are taken from the Triumph Performance catalog, as are the triple T and the mirrors at the end of the handlebars. Don’t repeat it, however, but this minimalist headlight comes from a Harley-Davidson Sportster….

The handlebars and adjustable levers come from the Triumph catalog

To design this boosted parallel twin to fit into this minimalist street tracker frame, Matt Capri bought a 2003 Bonneville engine on eBay and added a rebalanced and rebored 6.3mm crankshaft, retaining the 360 ​​° timing of the era. The stock cylinders were bored up to 92mm, the maximum value supported to avoid bursting the cylinders, a value that Matt discovered at his expense in the second year on the Salt Flats. This brought the original engine from 790cc to 988cc with dimensions of 92 x 74.3mm against the original 86 x 68mm.

The Bonneville engine has been boosted to 106 hp

Carrillo steel connecting rods are paired with Arias pistons, each fitted with custom axles that are 40% lighter and offset to minimize piston friction by counteracting the effects of the piston’s ultra-short skirts. The engine offers 11.5: 1 compression (compared to 9.2: 1 for the stock) although it still runs on a traditional gas pump, while delivering 106 hp to the rear wheel at 7,500 rpm on the same Dynojet test bench which recorded 61 hp for the same engine in its stock version. Indeed, that’s 75% more power on a motorcycle 25% lighter than a standard Bonnie, with an equivalent increase in torque since it goes from 64 Nm to 108 Nm at 4,200 rpm. It’s a lot.

The kit used by Capri for the engine

This forced Capri to raise the crown by 17 / 42T for a 19 / 38T, a modification that had allowed us to officially register a top speed of 246 km / h at Bonneville with a nearly identical engine. To take advantage of this substantial increase in torque and power, the standard 5-speed gearbox has been reinforced with a Barnett Kevlar multi-plate clutch and stiffer springs to ensure more progressive acceleration..

Key to this huge performance boost is the modified cylinder head of the eight-valve engine that tuner Rick Kemp worked on. The result is the passage of the intake valves to 36.5 mm, or 6 mm wider than the original and exhaust to 31 mm, or 5 mm more. There are also high-lift camshafts unique to South Bay Triumph. Finally, the cylinder head is fitted to the crankcases using a three-layer, rubber-coated MSL gasket to prevent any risk of leakage with this higher compression. A Swedish oil cooler limits the risk of overheating associated with all this extra power.

Food for the Street Tracker

Two 41mm Keihin FCR Flatside carburetors replace the stock 36mm. Equipped with a pair of K&N filters, they team up with the South Bay airbox which offers freer breathing for the extra revs brought by a remapped Triumph Performance ignition box. This adds 2,000 more revolutions over the 7,200 rpm programmed into the stock ECU of the Bonneville. Finally, Capri used the system designed for the Thruxton Cup with its double Lubricor exhaust on the right of the bike. The result is a muscular exhaust tone, without being aggressive.

The Street Tracker’s double silencer

In the saddle

Climbing aboard the Street Tracker we discover that the minimalist saddle is nevertheless comfortable, with the footrests positioned low enough, but set back to offer an excellent driving position for who must be the ultimate Triumph for the road.

The padded saddle of the Street Tracker

This ideal driving tool is not some sort of uber-maxi scooter, but a torquey Supertwin which is also incredibly easy to ride despite the considerable performance boost provided by engine preparation. To access it, simply open the fuel valve, drop the choke under the 26 ° C of the Californian sun and simply put on a few strokes of gas to prime the large Keihin carbs, press the ignition button and to prepare for the Triumph to come alive and settle into an idle at 900 rpm where you can almost hear each cylinder light up individually. Go first and be prepared for a surprise, as the engine softens as revs increase.

Street Tracker test under the Californian sun

In the city

Thanks to its slender build, a very open steering angle that makes U-turns in narrow streets a breeze, and a relatively high and upright position offering a breathtaking view of the roofs of cars, the Street Tracker allows to make an ideal path through the 70 suburbs that separate us from the metropolis of Los Angeles.

Street Tracker test in town

The Street Tracker is simply ideal for pulling up the queues of cars waiting at red lights or slipping through highway traffic or even crisscrossing the hills overlooking the Pacific Ocean where its rapid changes of angles and maneuverability take full advantage. meaning.

The Street Tracker is ideal for walking up the lines

The power curve is very linear and the acceleration punchy, with the deep sound of the two silencers offering the typical swingin ’60s accompaniment you should have on a British twin, as the front wheel lifts up and rolls over the pavement. at each red light which irresistibly turns into a GP. The carburettors offer an immediate response as well at the standing start as at the exit of a turn, but the result is even better on the medium revs, in particular at the level of the sound. It’s like back then, but much more powerful and much more torquey. It’s a true classic 21st century hotrod.

Accelerations are sharp and straightforward

On roads

The setting is optimal while the vibrations remain minimal even when you open the throttle wide in search of the breaker at 9,200 rpm accompanied by the typical sound of a British twin prepared and amplified by its two megaphones. The engine spins freely with perfectly adapted and immediate acceleration, but not jerky. The power supply, however, is not quite ideal in low revs and you can notice a slight hiccup or even transmission cuts when you accelerate hard below 3,500 rpm. Maybe the power supply still needs adjustment. This is where the real performance begins, the time for the Triumph engine to send torque to mid-range for impressive acceleration as the front wheel gets lighter in the lower two gears as the Acewell digital speedometer shifts. the 7,500 rpm bar.

Street Tracker test on the road

What marks you first, last, and all the time with the Street Tracker is the effortless growl of this motor, which quickly shifts gears around 7,000 rpm in any gear for you. allow you to take advantage of its ultra-flat torque curve. You really only have to play with the clutch to go up from first gear. The rest of the time you end up with the fastest, most precise and clean shifting I can remember on a Triumph Bonneville..

Gear changes are easy

Although the quick gear changes seem good in terms of optimizing the power delivered, the very smooth engine shows a serious appetite for high revs, around 8,000 rpm. Low-end power is muscular, but from 3,500 / 4,000 rpm higher when the squelch tone gets louder, the Tracker really takes off and picks up speed very quickly. Hold on tight so you don’t feel the handlebars shake in your hands as torque delivers over and over again, it’s just past 7,200 rpm, where the switch should normally do its job..

The Street Tracker on a curve

Change gears to 8000 and you’re back in the upper part of the power curve, accelerating even harder. Five gears in the gearbox are more than enough for such a powerful engine, especially when that ton of torque is so easy to access. This true street flat-tracker is both practical and fun to ride, although there is a lack of leverage on the clutch, the mirror at the end of the handlebars preventing you from moving your hand further back..

The Street Tracker is both practical and fun to ride

Cycle part

The only thing that really needs to be reviewed on the Street Tracker is the lower of the two exhausts, located too low and which rubbed the ground even at moderate angles. A month later and after I pointed it out to him, Matt Capri corrected the shot and sent me the photo of the new line placement. I guess ground clearance is not an issue when sliding from the back on a dirt track, but the good grip of the Avon Storm tires here invites you to keep your speed in the corners, which means ‘led to copiously filing the exhaust…

The exhaust line raised on the Street Tracker

I also found that it was quite easy to get out of the grip zone of the thin Avon 170/60 rear tire. But if that happens, just use the wide, flat handlebars to help get back on track. Phew! After this scare, I learned my lesson and rode the Tracker accordingly, braking hard to the point of the chord, then straightening the bike to get out quickly..

Rear tire lacks corner grip

Braking

The single 310mm front disc provides sufficient stopping power for such a light bike, even with the increased performance. It also helps to maintain precise and easy steering without being hampered by the added weight of a two-disc setup. The 6-piston Beringer caliper helps provide that good stopping power.

The Beringer front caliper ensures good braking

Conclusion

Available at the time from $ 35,000 depending on specifications, the South Bay Triumph Street Tracker is a classic California Hotrod with a certain seriousness: it’s thin, flexible, powerful, it accelerates, with few concessions in in terms of comfort and remaining faithful to the Cafe Racer tradition. It’s addicting to ride, a machine like yesterday’s, but with Matt Capri’s optimizations combined with modern suspensions and brakes. Its owner is really lucky…

The South Bay Triumph Street Tracker

Strong points

• Engine preparation
• Lightness of the motorcycle
• Braking and suspensions

Weak points

• Rear tire grip on the angle
• Exhaust line that limits the angles
• Low speed response

The South Bay Triumph Street Tracker technical sheet

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