Motorcycle Classics

1971 Triumph Bonneville T120R

1971 Triumph Bonneville T120R Fisher Racing Products
Claimed power: 57hp @ 7,000rpm
Tope speed: 130mph (est.)
Engine type: 649cc air-cooled OHV parallel twin
Weight (dry): 370lb (118kg) (est.)
MPG: 30-40mpg (est.)

The 1971 Triumph Bonneville T120R was the problem child of a shotgun marriage. It was responsible for Triumph missing that year’s U.S. sales season, and it just about bankrupted the company. So how did South African tuner and racer Nev Fisher turn this Ugly Betty into a custom Triumph motorcycle beauty queen?

The late Sixties Triumph Bonnevilles were, and still are, considered to be the best of the lot. But a major program of standardization was underway across the BSA Group, which also owned Triumph. For the 1971 season, BSA planned to use a new oil-bearing frame for both BSA and Triumph 650 twins.

However, the new Triumph frame had been designed around the BSA 650 engine, and when the first batches of frames were delivered to Triumph’s Meriden factory, assembly line workers found they couldn’t fit the Triumph engine in the frame without removing the rocker boxes from the cylinder head first.

The 1971 Bonnies were already behind schedule because of production delays caused by a shortage of parts — the result of teething troubles with a new computer system. The cumulative result was that very few Bonnevilles were at U.S. dealers for the critical April to June sales season. Other problems with the 1971 bike included a seat height only suitable for people over 6 feet tall, major frame failures caused by the center stand being mounted on the oil-bearing “sump,” and aesthetics only a short-sighted mother could love. The 1971 model is perhaps the least popular of all Bonnies.

Love conquers all

That didn’t stop Dave Carpenter from falling in love with his dad’s 1971 Bonneville. So much so, that a couple of years ago, he persuaded his father to sell it to him. “It dredged up all those feelings I had many years ago about riding those bikes back in the Sixties,” Dave says. But the reality of riding the old Bonnie, especially compared with Dave’s modern Triumph Thruxton, wasn’t how he remembered it. “This old Bonneville was in need of some serious work,” he says.

So he looked around for someone he could trust to carry out the restoration. Through a mutual acquaintance, he learned of Nev Fisher, a racer and bike builder in East London, on the Eastern Cape seaboard of South Africa.

Nev has been racing motorcycles for nearly 30 years, starting with, coincidentally, a Triumph Bonneville. Although racing against modern machinery, Nev more than held his own and also won an inter-regional classic championship in 1997. Switching more recently to Ducatis, Nev has taken two more inter-regional titles and has recently proved very competitive on a modified Ducati 748 of 853cc. Nev does all the race prep and tuning himself.

In between his racing exploits, Nev runs a company that manufactures strapping materials, while at the same time he’s built a thriving business importing Triumph and Ducati competition parts. However, the value of the South African rand on foreign exchanges also means Nev finds it more cost effective to fabricate many of the parts he needs in his own shop, Fisher Racing Products.

The relationship between Dave and Nev developed over the internet, but perhaps the clincher was that both are committed Christians. With this common bond, Dave decided he could trust Nev to revitalize his dad’s old bike — even though Nev was, literally, on the other side of the world. The result of the collaboration is one of the sweetest Triumph café racers around.

Building blocks

Essentially the only parts from the donor bike that Nev planned to use for the project were the engine and frame, so that’s what Dave shipped off to him from his home in Langley, British Columbia, Canada. Nev first stripped off the passenger footpeg frame loops and the troublesome center stand mounts. The rear shock mountings were moved to raise the rear end by an inch, and lugs for a steering damper, custom rear light cluster and rearset footpegs were added. Nev installed the front end from a 1969 Bonnie with custom-made aluminum triple clamps to lower the front by 2 inches. Inside the forks are modified springs, while a FRP fabricated fork brace and steering damper keep the front end straight and true. A fresh coat of 2-pack paint completed the frame cosmetics.

The earlier 8-inch twin-leading-shoe front drum brake from the 1968-70 Bonneville works better than the 1971 version, so that’s what Nev mounted to the 18-inch WM4 Akront aluminum rim, courtesy of 8-gauge stainless spokes. Inside the drum, the shoes are bonded and riveted and the drum drilled to reduce unsprung weight. At the rear, a similar size Akront rim hangs from a 1971 single-leading-shoe Triumph conical hub, machined to replicate a Manx drum brake. Hagon shocks with exposed springs provide suspension. Adjustable clip-on bars finish off the cycle parts.

The drive train was extensively modified. Nev stripped the engine down and rebuilt it with standard T120 con rods that had been weighed, balanced and polished, topped with 11:1 compression racing pistons. These went into a bead-blasted crankcase venting through a 5/8-inch breather on the timing case. Timing gears were lightened and indexed. Nev then ported the cylinder head, lightened and polished the rockers, and located them accurately on the rocker shafts with shims rather than the stock spring location arrangement. Aluminum pushrods drive the rockers, which act on Black Diamond racing valves running in bronze valve guides, closed with PM racing springs. Alloy collets and retainers replace the stock steel items.

To improve lubrication, Nev fitted a Morgo rotary gear oil pump and a Norton Commando-style cartridge oil filter, with an oil cooler, high pressure relief valve and SRM billet aluminum rocker feed. Primary drive is by belt to a dry diaphragm spring clutch with the primary cover extensively machined for cooling and weight saving. Final drive from the 4-speed Triumph gearbox is taller than stock at 2.35:1 versus the original 2.47:1 for more relaxed cruising.

Feeding the engine is a pair of 32mm Mikuni carbs, while sparks are provided by a 12-volt alternator/battery electrical system and Boyer electronic ignition. Exhaust gases exit via a pair of pipes and mufflers Nev made himself, the reverse megaphone end pieces being turned out of aluminum billet.

Dave’s wife, Pam, is a keen pillion rider, so Nev fabricated a seat base long enough for a custom dual seat, and also fabbed matching rider rearset pegs and passenger pegs, the latter attached to a custom hanger. The tail lamp cluster and bikini fairing are Ducati parts, the former from a 999 and the latter a TT2 item. The gas tank is a stock Bonneville unit, but the side panels are handmade from magnesium alloy sheet. A rubber mounted aluminum instrument panel holds the speedometer, tach and an oil pressure gauge.

On the road

Starting the Bonnie is easier than you’d expect, given the 11:1 slugs; and the combination of Boyer sparks and modern Mikuni carbs means it usually fires first kick, according to Dave. Of course, with me watching, it takes six or seven swings before the Bonnie erupts with a snarling roar. The engine is remarkably quiet mechanically, but the custom mufflers emit a solid boom with just a hint of a crackle.

I follow Dave along one of his favorite roads, and it’s soon apparent that the born-again Bonnie is a riot to ride. He’s obviously enjoying himself, and we pull over at a quiet country deli for lunch.

“I’d forgotten that whole feeling,” he says. “It’s very raw and a definite turn-on. You know you’re on a machine that’s definitely not acting its age. The extra power from the TT pistons, Fisher tuning, porting and custom balancing gives you that extra torque and horsepower you were looking for in 1969.”

A tighter rake angle — due to dropping the forks 2 inches, raising the bike’s rear end, and some of Nev’s secret internal spring work — results in exceptional handling, reports Dave.

“This thing lives for corners,” he says. “As far over as I could get, I couldn’t ground the pipes or the pegs. It just bred a confidence that I don’t remember back in the good old days.

“It works surprisingly well for a 40-year-old design,” he continues, “and gives you a bit of that natural sport bike cornering. There is very little unexpected over- or understeer. The damper also keeps things very predictable in the higher-speed bumpy sweepers.

“You can feel all the unsprung weight that is missing when you flip side to side. There’s not a lot of resistance. To be honest it just keeps begging for more speed. At 90mph sweeping uphill, you can tell it’s just getting started.”

And speed it has aplenty. Dave reports that the engine has “surprising torque,” even though he’s limited to 5,000rpm during the break-in period. “There’s much more than I ever remember and I haven’t had a chance to ring it out in the powerband yet,” he says. “It pulls very nice in any gear. Powering through corners is very natural. Vibration is surprisingly absent.”

The soundtrack is pretty good, too. “The sound is pure magic. After my first ‘real’ ride I was addicted,” Dave reports. “I hated to kill the ignition when I got home. I just wanted to sit there and listen to those pipes. The aesthetics are also very cool. Looking at the dash and cockpit puts you right in the café zone. What would the world be like if Triumph had put something like this out in 1971 and gone ‘café’?”

Well, café racers are certainly back in style, and having the Triumph name on the tank is no bad thing. Maybe Nev Fisher is on to something … MC

  • Published on Jun 8, 2010
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