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1963 Triumph Bonneville

The 1963 Triumph Bonneville was essentially a brand-new bike. Not quite designed from a clean slate, but nearly every part was new and/or improved. Gone were the days of adjusting the primary chain by loosening the gearbox then swiveling in its mounts, only to have to readjust the rear chain afterwards. Now it was a simple adjustment, modern. Modern too was the new Alternator and Points electrical system, gone was the antiquated magneto and dynamo, those days were gone, this was a new day, a brighter day! And brighter it was. The 1963 Triumph Bonneville and all the new unit-construction 650 Triumph motorcycles were an instant hit! It had it all: stunning performance, world-class handling and drop-dead good looks!

The 1963 Triumph Bonneville was again, as always (except the 1959 Triumph Bonneville), styled like its sister-bike, the Triumph TR6, rather than the dowdy Triumph Thunderbird.

For 1963, again the Triumph Bonneville 650 came in two basic models: the T120R was the road model; and the T120C was the off-road/street scrambler (what might later have been referred to as an Enduro). This was the first year Triumph 650 twins were stamped with a model prefix on their engine numbers (ie: T120R & T120C). Every 1963 Triumph Bonneville was painted the same: Alaskan White, one of the only years Triumph Motorcycles used a solid color, rather than a 2-toned color combination. While the tank was painted solid white, the fenders had gold stripes running lengthwise down their centers, lined in black pinstripes.

The 1963 Triumph Bonneville was the first year of unit construction, starting with Engine #DU101, and it saw nothing short of a major overhaul of nearly component. Some pieces from the pre-unit engine were retained but most of those were modified for duty in the new powerplant. An all new cylinder head casting added a 9th head bolt (5/16″) between the cylinders, and a relocating of the other 8 head (3/8″) bolts to help cope with the rising compression ratio. More metal was added around the valve seats to prevent cracking (a problem with the old 8-bolt heads of the pre-unit 650s) and allow for larger valves (although valve sizes remained unchanged, for the time being). Deeper finning and the twin carbs now bolted to intake spigots screwed into new splayed intake ports. This became the trademark ‘Triumph Bonneville look’.

New unpolished rocker boxes now had finning and steel spring clips keeping the valve inspection caps from unscrewing under vibration. The cast iron cylinder block was identical to the pre-unit piece with the exception of the reworked 9-head bolt pattern on top and it could be bolted to a pre-unit bottom end.

Much thought was put into the ‘look’ of the engine. Triumph Motorcycles’ engineers at the Meridian factory in England wanted the all-new engine to clearly display its lineage with, and thus is justification to be called a Triumph Bonneville. Additionally, they didn’t want to have to invest in all new tooling. Lastly, Edward Turner, the father of the vertical twin and the designer of the seminal 1937 Triumph Speed Twin, was still on the board of directors at Triumph Motorcycles owner, BSA, was enamored with his own design, and didn’t mind seeing it improved, but never replaced. He would retire the following year after the release of the 1963 Triumph Bonneville, in 1964.

ABOVE: 1963 Triumph Bonneville T120R, Roadster with down pipes. Note no air filters.

So, the basic layout was retained: timing gear on the right, primary and clutch on the left, transmission shifter and kick starter on left, and they ‘styled’ the transmission and timing chest to resemble the basic shape of the old pre-unit Triumph 650 engine. The primary cover, while similar in basic shape, now sported a sharp-looking Triumph logo in a highly-stylized ‘sideways coma’ cast right in. This became a highly-recognized Triumph trademark over the years.

Inside, a new crankshaft was fitted, the right end (timing side) of which now rode in a modern oil seal within the timing cover, rather than the antiquated phosphor-bronze bushing of the old pre-unit design, which now gave better oil pressure to the crank journals. Cams were now E4819 inlet and E4855 exhaust, with the exhaust cam driving the tachometer on the left and the twin ignition points (contact breakers) on the right, located under a round chrome cover secured to the timing chest with 2 screws. A new plunger oil pump, driven off the inlet cam gear, now worked in reverse from the pre-unit design (ie: the feed chamber was now on the right instead of the left, as before).

On the drive side (left), the primary case, now integral with the crankcase, rather than a separate bolt-on component, now longer played host to the left-side foot peg. Inside was a completely new 3/8″ duplex chain, with 29 teeth on the engine sprocket and 58 teeth on the clutch basket, and it was now adjustable via a rubber-coated slipper adjusted by a bolt on the outside of the cover. The clutch, already taxed to its limits, was beefed up with an extra friction plate (now totaling 6), stronger springs, a new clutch-actuator mechanism and a new 3-vane rubber clutch shock absorber. While the external case was, of course, all new, the internals of the transmission (gearbox) changed very little from pre-unit to unit. The front sprocket was now 19 teeth and the rear wheel sprocket has 46 teeth. The speedometer took its drive off the layshaft of the transmission.

The 1-1/16″ Amal Monobloc carburetors of the ’62 were retained, however clear plastic fuel lines now replaced the older black ones. There were still no air filters, just open bellmouth megaphones. The new 6-volt electrical system was state-of-the-art for the day. An alternator, contact breakers and two coils (Lucas MA6) replaced the dynamo (lights) and magneto (spark) of older bikes. The alternator had an energy transfer coil that allowed the bike to be started even if the battery was dead. The 7″ headlight, no longer QD (Quickly Detachable), housed the Lucas 2AR ammeter. The brakelight switch was moved to the chain guard.

As substantial and the new engine was, it was only half of the story of the new 1963 Triumph Bonneville. The frame was entirely new and addressed the shortcomings of the previous ‘duplex’ frame. Still made of a bolted-up front and rear section, of standard (for the day) brazed-lug construction, it featured a single beefy 1-5/8″ front downtube extending down from a heavy steering head lug which, in turn met with the heavy back bone and a second bracing member, running under the tank. This solved the primary weakness of the duplex frame, cracking in the steering head-area. Steering angle was retained at the same 65 degrees. The swing arm pivot was also beefed-up, with a large forged lug brazed to the thick vertical frame post and bolting to the rear engine mounting plates for added stiffness.

The 1963 Triumph Bonneville is the only year when the foot pegs attached directly to the frame. All other years attach to the rear engine mounting plates. This year, only the brake pedal pivots on the left engine plate. Passenger (pillion) pegs now attached to mounting plates bolted to the rear subframe, to which the mufflers were also strapped on T120Rs. T120C off-road models came with skid plates to protect the engine and delicate oil lines.

Girling shocks were rated at 145 lb/in for UK and Export, and 100 lb/in for the US market. While the front forks were largely carried over from 1962, a new top yoke (triple clamp) accommodated rubber bushed detachable handlebar mounting clamps. Handlebars were brought down from 1″ to the industry standard of 7/8″, although the mounts would accommodate either, with the aid of shims. UK models got low bars and US models got high bars. The twin carbs were now controlled by two separate throttle cables rather than one running through a splitter. Hand grips were black checkered plastic and made by Amal.

Wheels and tires were now 18″ front and rear, with a 3.25 X 18″ ribbed Dunlop front tire on a WM2 rim; and a 3.50 X 18 Dunlop Universal tire on a WM3 rim out back.

The net effect of it all was a commendably-stiff, superbly-handling motorcycle frame. From this point on, Triumph motorcycles were renowned as one of the best-handling motorcycles in the world. Even after the onslaught by Honda, Yamaha, Kawasaki and Suzuki, despite clearly winning the technology race, it took years for the Japanese to get their bikes to handle as well as a Triumph motorcycle. This frame was so good, it stayed in service, pretty much as is, until 1970, when it was replaced by the controversial and much-unloved Oil-in-Frame frame (also known as an “Oiler”).

The seat was now hinged, rather than bolted down, allowing access to the battery and oil filler. The seat itself was gray on top, had white piping, black sides and gray trim along the bottom edge. The front fender carried over from the 1962, but the rear fender was all new, with an embossed ridge running down the center. The gas tanks now mounted on thick rubber bushings to twin mounting brackets cast into the steering head lug. Again, US/Export tanks were 4 Imp. gal. and US tanks were 3 Imp. gal. The new oil tank matched the shape of the left side cover, both painted black, the latter carrying the light switch and ignition switch. UK models still had no tachometer, although all had the cable drive on the left end of the exhaust cam. This cable drive was not right-angled, so the cable shot straight out the side of the engine and was forced to quickly bend to reach the tach. This looked sloppy and broke cables.

It would be addressed soon enough. Such is the story of the Triumph Bonneville. It was a work in progress, never finished, but never changed. Improved through evolution, not revolution. The 1963 Triumph Bonneville was the first in a long line of great Triumph motorcycles, the big twins. While even they would not be enough to save the British motorcycle industry, already fracturing around the edges by this time, or even Triumph for that matter, the Triumph Bonneville did endure longer than any other classic British motorcycle.

1963 Triumph Bonneville T120C STREET SCRAMBLER

ABOVE: 1963 Triumph Bonneville T120C, Street Scrambler w/high pipes.

BELOW: 1963 Triumph Bonneville T120C tank w/4-bar tank rack & single-gauge, tach-only.

1963 Triumph Bonneville TT SPECIAL

The 1963 Triumph Bonneville T120C TT Special was really the brainchild of US West Coast distributors, Johnson Motors, also known as “JoMo”. The factory had taken way too long to introduce pure competition versions of their popular Bonneville line. Edward Turner was opposed to the idea, but burgeoning demand for such machines in the US was impossible to ignore.

Introduced in 1963, the TT Special was essentially a stripped-down Triumph Bonneville with high pipes & special tuning. They dominated American TT Scrambles & Desert Racing for years. Nothing could touch them. The TT Special appeared in the catalog from 1963 through 1967, during which a total of around 3,500 were built.

And no wonder. With big carbs & a 11.2:1 compression ratio, the TT Special pumped out 52hp! For 1963, the TT Special got larger 1-3/16″ Amal Monobloc carburetors with 330 main jets & an elegant high exhaust, that ran one pipe all each side, above the engine cases, with heatshields protecting the riders’ legs. While the compression ratio was claimed to be 12.0:1, it was in reality about 11.2:1. The cams were identical to those used in the T120R. Early models came without air filters.

Ignition was by AC energy transfer (ET) run directly off the alternator, sans battery. Rim sizes were 19″ front & 18″ rear shod with 3.50 X 19 & 4.00 X 18 Dunlop Trials tires. The only gauge was a tachometer (rev counter) mounted on the top yoke. To top if all off, strangely, the TT Special came with the chromed parcel rack on the top of the tank, the same as the road models.

1963 Triumph Bonneville  SPECIFICATIONS

Bonneville T120R

Bonneville T120C

Engine type


Bore & Stroke




Engine output

Primary drive

Primary drive sprockets



Ratios, overall:

1st, bottom



4th, top

Final drive

Final drive sprockets

Frame type

Suspension, front

Suspension, rear

Brake, front

Brake, rear

Tire, front

Tire, rear

Fuel Capacity


Seat height

Ground clearance

Weight, unladen

Roadster, low pipes

Street Scrambler, high pipes

Air-cooled OHV vertical twin

649cc / 40.0 ci

71mm X 82mm / 2.79″ X 3.23″

8.5:1 (T120) / 11.2:1 (TT Special)

2- Amal Monobloc 1-1/16″ / 1-3/16″ (TT)

Battery & coil (T120) / Energy Transfer (TT)

46 bhp @ 6500 (T120) / 52 bhp (TT)

3/8″ triplex chain X 84 links

29T X 58T

Multi-plate, wet

4-speed constant-mesh, right-foot shift





5/8″ X .400″ X 3/8″ chain X 106 links

19T X 47T

Brazed lug, full-cradle, single downtube

Telescopic fork, hydraulic damping

Swing arm, 2 Girling dampers

8″ SLS drum, full width

7″ SLS drum

3.25″ X 19″ Dunlop

4.00″ X 18″ Dunlop

2.5 Imp gal (US) / 4 Imp gal (UK & export)

54.5″ / 140.3cm

32.5″ / 77.5cm

5.0″ / 12.7cm

363 lbs / 165 kg