Triumph T120 Bonneville 


Make Model

Triumph T120 Bonneville 650


1963 - 64


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 MA6 alternator with 2 coils



Max Power

34 kW / 46 hp @ 6500 rpm


Wet, multiplate


4 Speed, constant mesh

Final Drive

Chain, 106 links

Gear Ratios

1st 11.80 / 2nd 8.17 / 3rd 6.76 / 4th 5.84:1
Frame Single front downtube, second bracing member running under tank
Steering Angle 65o

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 18, Dunlop Universal

Rear Tyre

3.50 x 18, Dunlop Universal


1403 mm / 55.2 in

Seat Height

775 mm / 30.5 in

Ground Clearance

127 mm / 5.0 in

Dry Weight

165 kg / 363 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's Speed Twin had been one of the bikes that helped to set the pace before the war. After the conflict, the SOOcc Speed Twin spawned many descendants, from 350 to 7S0cc 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 110, 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 into oblivion.