Triumph T120 Bonneville 650


Make Model

Triumph T120 Bonneville 650


1960 - 61


Four stroke, parallel twin, OHV


649 cc / 39.6 cu in
Bore x Stroke 71 x 82 mm
Compression Ratio 8.5:1
Cooling System Air cooled


2 x Amal 1 - 1/6" carburetors


Lucas magneto



Max Power

34 kW / 46 hp @ 6700 rpm


Wet, multiplate


4 Speed, constant mesh

Final Drive

Chain, 101 links

Gear Ratios

1st 11.90 / 2nd 8.25 / 3rd 5.81 / 4th 4.88:1
Frame Twin steel downtubes

Front Suspension

Telescopic forks, hydraulic damping

Rear Suspension

Swingarm, twin Girling dampers

Front Brakes

8" SLS drum

Rear Brakes

7" SLS drum

Front Tyre

3.25 x 19, Dunlop

Rear Tyre

4.00 x 18, Dunlop


1400 mm / 55.25 in

Seat Height

770 mm / 30.5 in

Ground Clearance

127 mm / 5.0 in

Dry Weight

183 kg / 403 lbs

Fuel Capacity 

US: 13.6 L / 3.6 US gal / 3 Imp gal / UK and other Export: 18 L / 4.8 US gal / 4 Imp gal

Triumph announced the ultimate expression of Edward Turner's 650cc pre unit twin in September 1958 ready for the 1959 season. Named the Bonneville in recognition of Triumph's record breaking success at the salt flats of the same name, the new machine replaced the Tiger 110 at the head of the sporting Triumph range.

The significant difference between it and the Tiger 110 concerned the cylinder head which was fed by two carburettors on splayed inlets together with a higher compression ratio, resulting in a claimed 46bhp.

The 1960 season machines adopted a new duplex frame and lighter styling, losing the headlamp nacelle and partially valanced mudguards which had graced the 1959 models, with further detail revisions to the frame occurring for the 1961 model season.

Triumph's Speed Twin had been one of the bikes that helped to set the pace before the war. After the conflict, the 500cc Speed Twin spawned many descendants, from 350 to 750cc capacity. Above all others, the 650cc Bonneville became the bike that set the standard throughout the late 1950s and 1960s - the era of the Rockers and Cafe Racers.

The first 650cc Triumph appeared in 1949, when the softly tuned 6T Thunderbird showed its pace at the Monthlery speed bowl before going on sale the next year. The model was an excellent tourer.

In 1951, a Thunderbird racer, equipped with twin carburettors, hot cams and high-compression pistons, reached 132mph at Utah's Bonneville Salt Flats. A few years later, in 1956, Johnny Allen achieved 214.4mph, a record accepted by the US authorities, but the world governing body refused to acknowledge it. Americans continued their efforts, and two years later a specially prepared Tiger I 10 managed to achieve over I47mph, ridden by Bill Johnson. The speed was good enough for a class record. That was in 1958, and the venue once again was Bonneville.

The first Triumph machine to bear the Bonneville name appeared in 1959. Based heavily on the Tiger I 10, the T120 was fitted with the twin carburettors, together with the hot E3134 inlet cam. With a power rated at 46 bhp, the model was already good for a comfortable I I5mph - but the engine had the potential to be tuned a lot hotter.

From 1963 they gained a new frame, with extra bracing for the swinging arm and steering head and a new compact power unit. The steering angle was changed and improved forks were adopted.

All these improvements helped the Bonneville to match its rivals' all-round performance. In the styling stakes, however, it had no equal. Where the contemporary BSA was worthy but perhaps a little stolid, and Norton's offering lacked the absolute glamour of its racing forebears, the 650 Bonneville oozed get-up-and-go. On the race track, it got up and went! In 1967 and 1969 it won Production TTs and British 500 mile races. In 1969 the works TI00R achieved a 1/2/3 in the

Thruxton 500-miler, covering three more of the top seven places.

In the opinion of many, the 1968 Bonneville is the best of the breed. With good handling and more reliable electrics than its predecessors (including a new ignition), all the good features were there in a package that was hard to beat.

But it was almost the end of the line. The 650 twin would only survive a scant three years before it was replaced by a new 750cc and Triumph began its slow slide.