Triumph Tribute GP Racer
Engine: 498cc air-cooled OHV parallel twin, 63mm x 80mm bore and stroke, 8.25:1 compression ratio, 42hp @ 7,000rpm (T100C spec)
Top Speed: 109mph (T100C period test)
Carburetion: Two Amal 376 Monobloc w/remote float
Transmission: 4-speed, chain final drive
Electrics: 12v battery total loss, Lucas magneto ignition
Frame/Wheelbase: Single downtube steel cradle frame/55.1in (1,397mm)
Suspension: Telescopic forks front, sprung hub rear
Brakes: 8in (200mm) SLS BSA drum front, 7in (175mm) SLS Triumph drum rear
Tires: 3 x 19in front, 4 x 19in rear
Seat height: 29.9in (760mm)
Weight (dry): 320lb (145kg)
Fuel capacity: 3gal (11.5ltr)
It all began during a simple conversation between two friends about Triumph’s legendary Grand Prix race bikes.
During a discussion with Bob Klassen about how much we both admired the famous Triumph GP race machines built between 1948 and 1950, I pointed out that I had a rigid Triumph frame and parts of an all-alloy 500cc T100 engine sitting around. Bob mentioned he had a Triumph fork, a BSA Gold Star 8-inch front hub and a Borrani alloy rim, a pair of Amal carburetors with a remote float, a magneto, and parts of a gearbox. What happened next surprised both of us: We decided to pool our parts, share the expenses and build a “tribute” Triumph race motorcycle.
As a paraplegic, there’s no question that I’ll ever be able to ride the machine — I won’t. But our cooperative efforts returned components that were sitting in our respective Calgary, Alberta, Canada, garages back in service. But before we learn more about our project, let’s go back to the beginning for some background about Triumph GP racers and some of Triumph’s other speed efforts.
In 1946, Freddie Clarke, head of the experimental department at the Meriden factory, constructed Triumph’s first postwar racer. The prototype was based on a Triumph Tiger T100.
During World War II, Triumph had developed a portable generator set for the Royal Air Force. Power came from a T100 twin, but made with aluminum instead of cast iron cylinders and heads to keep weight and operating temperatures down.
Clarke removed the standard iron barrel and head from the 500cc twin-cylinder engine and replaced the components with the generator engine’s unique alloy square barrel and head.
With Irishman Ernie Lyons aboard, the first all-alloy 500cc Triumph racing motorcycle took the win at the 1946 Manx Grand Prix. According to Lindsay Brooke, writing in his book Triumph Racing Motorcycles in America, the GP was given a “reluctant blessing” by Triumph boss Edward Turner.
“The GP was Triumph’s first dual-carburetor 500, and its specification was impressive.” Brooke states. “The bike weighed just 310 pounds, even with its standard 17-pound sprung hub rear wheel, which gave a maximum 2 inches of suspension travel. Despite the infamous hub, the GP came ready to race, with megaphone exhausts, Ferodo clutch inserts, an external cartridge-type Vokes oil filter, dropped handlebars, rearset pegs, aluminum mudguards, Dunlop alloy rims and racing tires, 8-inch brakes, racing pillion, tachometer, and a 4-gallon fuel tank with quick-action filler cap.”
The GP was a limited production motorcycle, available to privateer racers only from 1948 to 1950. According to the blog Wayne’s Triumph Motorcycles, actual production numbers are hard to peg. However, in a post about the GP machines he says, “… it appears from Triumph records that only 151 were built, along with 15 spare motors with only about 30-35 GPs sent to North America.”
In a 1951 Triumph booklet dubbed Tuning the 1951 Triumph Tiger 100, the maker claims, “[The T100] has always responded well to the efforts of amateur tuners, and has taken a successful part in competitive events in all parts of the world.”
The copy continues: “The 1951 Tiger 100 is a new model incorporating a new engine of advanced design with an aluminum alloy cylinder barrel and head, and many other features calculated to provide enhanced performance. This machine is both lighter and faster than its predecessor, and although it is supplied from the factory to roadster specification only, a special feature is the provision made in its design whereby it can, at a most reasonable cost, readily be converted by the knowledgeable owner from its standard form to racing specification.”
The Racing Kit
Enter the special “Tiger 100 Racing Kit,” a package of go-fast parts developed by Triumph’s experimental department with input from salesman and racer/tuner Pete Colman of Johnson Motors of Los Angeles, California. Priced at around $100, the race kit could be supplied to an owner on receipt of their engine and frame numbers. The components were available separately, but the race kit came complete with either 8.25:1 or 9.5:1 compression ratio pistons, racing profile camshafts and valve springs, twin Amal Type 6 carburetors with a remote float and dual throttle cables, a Smiths 8,000rpm tachometer, a 1-gallon oil tank with a quick-release cap, exhaust pipes with megaphones, footrests, a handlebar, a number plate, a short rear brake rod, folding kickstart lever and a set of gaskets.
Race kit aside, Triumph did build one more production competition model based on the rigid frame Tiger 100. In a brochure published Oct. 24, 1952, for the 1953 model year, Triumph shows a Tiger 100 and Tiger 100C. The T100C was prepared from the factory for racing, complete with dual Amal carbs, high compression pistons and racing cams. Horsepower was rated at 42 at 7,000rpm when fitted with a racing exhaust, and only 560 of the crackerjack T100Cs were produced.
Building our bike
All of this knowledge left Bob and me contemplating our pooled lot of parts, and our conversations circled around exactly what we wanted to build. Without the GP racer’s alloy square barrel and head, where the exhaust headers exit parallel to each other instead of being splayed out as on the T100 engine, we determined not to build a replica. Instead, a tribute bike seemed the most practical way to go.
Early in 2015 work began on the frame. I’d located a rigid 1948 Triumph frame online in the fall of 2014. The seller was based in Ontario, and he’d found it rusting away in a pile of scrap he’d purchased from a defunct machine shop. The frame’s lower seat downtube had for some reason been cut away, but apart from that it was relatively straight and in good condition.
Luckily, I had years ago rescued a front Triumph frame half that was missing the neck. The lower seat downtube was harvested from this, and an internal slug was turned on the lathe, fit inside and the tubes welded together.
Bob handcrafted a rear brake pedal mount and rearset footpeg mounts, and these were welded to the lower frame rails. Cory Brewster of Brewster West Industries in Turner Valley, Alberta, handled the frame welding in trade for some labor from Bob, as Cory was building a Triumph bobber of his own at the time.
While visiting John Oland at Motoparts in Edmonton, Alberta, Bob purchased a used Mark II Triumph sprung hub. In excellent condition, the hub was taken apart to the point of not removing the springs, and both it and the 8-inch BSA front hub were sent for powder coating. If it’s black on this machine, it was powder coated by Rite-Way Powder Coating in Calgary, Alberta. The sprung hub bearings were cleaned and repacked with fresh grease, and even the original sprocket and brake shoes were in serviceable condition.
Wheels, suspension and more
The BSA front hub was laced to the 19-inch Borrani rim using stainless spokes ordered from Walridge Motors, while the sprung hub required a specially drilled WM3-19-inch flanged Morad alloy rim and stainless spokes from Central Wheel Components Limited in the U.K. The tires are Avons, a Roadrunner at the back and a Speedmaster up front.
To anchor the front end, Bob modified a set of early 1950s Triumph hydraulic forks by fitting later-style — and far superior — internal components. A GP-style fork brace came from Ace Classics, and a friend donated a new-old-stock chrome fender that suited the project. It bolted to the GP brace, and the lower stay was made from scratch. In another friend’s garage, Bob found an undrilled chrome fender blank that was long enough to extend from the lower frame mounting point to a good distance around the tire. All of the rear fender stays came from Ace Classics.
Turning to the engine, I had a set of cases that were fitted with the T100 alloy barrel and head. They were empty, but a set of new-old-stock high-lift E3134 Triumph camshafts were on my shelf, and a donor crank, connecting rods and cush-drive spring and sprocket were located in New Mexico. What was thought to be a rusted and seized up crank turned out to be a jewel, as the oil had long ago hardened between the white-metal big ends of the connecting rods. After cleaning the journals were spotless, and when the rods were measured with Plastigage the big end clearances were within tolerance, although new piston end bushes were installed.
By some miracle, the alloy cylinder block had never been bored oversize, so a set of 0.020-inch oversize pistons was ordered from British Only Austria. The cylinder head had one damaged fin, but Derek Pauletto of Trillion Industries in Calgary patched that up. The rebore and some headwork was done by Motoparts in Edmonton.
On the intake side of the engine a manifold kit was sourced from Hal Hall Products on eBay. Hung on the manifolds is a set of chopped 376 Amal Monobloc carburetors. The remote float is the correct Triumph racing kit item. The exhaust pipes are meant to fit a unit-construction T100 Triumph and measure 1-1/2 inches at the spigot before necking down to 1-3/8 inches for the rest of the run. These are capped with short, internally baffled megaphones from Cone Engineering.
The gearbox is a 1940s Triumph shell retrofitted with later internals and a needle bearing modification on the layshaft. None of this was terribly easy, but, to quote Bob, “None of this really fought us, either. The bike just came together rather fluidly, and it always had a great look to it right from the start.”
Many used pieces to put the gearbox together came from my parts bins, including the clutch. Even the tall Triumph 3T seat springs were in my inventory of pre-unit Triumph bits. The saddle is a reproduction Dunlop rubber affair from Sammy Miller Products, and the pillion was a relatively inexpensive eBay find. Inverted Norman Hyde M bars give the appropriate riding stance with the rearset pegs, and restorer John Whitby painted the competition-style Triumph 3-gallon gas tank three different shades of blue.
The oil tank is from a pre-unit BSA. It’s been modified to increase capacity and accept the Triumph oil lines and scavenge feed for the overhead valve gear. To complete the racer look, we found a tachometer-drive gearbox on eBay, and the Smiths RC126 0-8,000 tachometer came from Andy Henderson of Vintage British Cables.
The Triumph has been wired with lights, and all the wires are hidden in the frame. There’s a tiny chrome headlamp tucked behind the front number plate while a small 12-volt battery is specially mounted directly behind the gearbox.
With some 750 miles on the tribute Triumph, Bob can report that it tracks perfectly straight and the front end feels solid and well planted. The sprung hub gives a modicum of travel without any evidence of squirrelly handling around corners. “The bike hasn’t been broken in,” Bob notes, “but it’s a very smooth motor that’s briefly touched 5,000rpm, and it gives the impression it’s eager to go beyond that if you wanted it to. The gearing is such that 60mph is about 4,100rpm.”
It won’t be out wheel to wheel at a Grand Prix race any time soon, but it was never meant to. It’s a tribute and a bike built between friends, and the experience shared is better than the sum of its parts. MC