Tubular steel, double front downtubes, oil bearing large
tube backbone
Front Suspension
Telescopic forks
Rear Suspension
Swingarm, Girling shocks, 3-way spring preload adjustable
Front Brakes
Single 254 mm disc, 1 piston caliper
Rear Brakes
Single 254 mm disc, 1 piston caliper
Front Tyre
3.25-19
Rear Tyre
4.00-18
Rake
28o
Trail
109 mm / 4.3 in
Wheelbase
1422 mm / 56 in
Dimensions
Length: 2220 mm / 87.5 in
Width: 840 mm / 33.0 in
Seat Height
813 mm / 32.0 in
Dry Weight
200 kg / 441 lbs
Fuel Capacity
18.2 Litres /
4.8 US gal / 4.0
Imp gal
Consumption
5.5 L/100 km / 18 km/l / 42 US mpg / 51 Imp mpg
Top Speed
190 km/h / 118 mph
When Edward Turner was pencilling
his design for the Triumph Speed Twin way back in the mid-1930s he could
scarcely have dreamed that the same basic design would be used to power a
superbike of the 1970s, the Triumph Bonneville 750. The fact that the Bonneville
lasted so long is a tribute to the men at Meriden who, when their factory
was threatened with closure during the early 1970s, engaged in a marathon
sit-in which saved the works, their jobs, and their beloved Bonneville for
another decade.
By 1978, however, the Bonneville
was something of an anachronism in the world of motor cycling. It had an
old-fashioned twin-cylinder, pushrod engine in a world dominated by
multi-cylinder machines from Japan. Astonishingly, the Bonneville was still
the best selling 750 in Britain during 1978 in spite of the fact that this
was one of the most competitive classes on the market. Much of
this success was due to the absolute simplicity of the Bonneville. Weighing
about 395lb it was about a hundredweight lighter than most of its Japanese
rivals and with a crankcase measuring about 14 inches across it was a good
eight inches narrower than the bulkier Japanese fours.
This light weight and slim build
also meant that the bike's manoeuvrability and handling were far superior to
most of its rivals, a fact that went down well with British riders confined
to roads narrower, shorter and more crowded than those of their colonial
cousins.
The powerhouse of the Bonneville
is a straightforward piece of machinery. Two cylinders, each measuring 76 mm
by 82 mm, give a total capacity of 744cc-the original Bonneville models,
incidentally, were of 650cc but were uprated for more power and torque—while
the valves are operated by pushrods. Two Amal carburettors provide the fuel
for the 8.6:1 compression ratio motor, giving a power output of 49 bhp at
6200 rpm, not a great deal by modern Japanese standards. Where the
Bonneville scores over the Japanese multis, however, is that the engine
offers usable torque even at the lowest revs. The only serious problem
surrounding the Bonneville is the classic one common to most parallel
twins—vibration. At high revs the bike vibrates quite severely, sending
tingling sensations through the rider's arms and shoulders which at times
may even become painful.
Another criticism levelled at the
Bonneville is that its engine leaks oil. Models produced by the Meriden
cooperative, however, are a far cry from those oldoil burners of the 1950s
and the average owner has little to complain about in that respect.
Visually the Bonneville changed
little over the years. It retained that lean and lithe look that is so
typically British and which made it so popular over the years. The paint
finish on the tank, much of it hand applied at the factory, is superb.
Indeed, the bike is immaculately finished, living proof of the loving care
and attention that went into the building of these machines.
The Bonneville may not have had
the performance or sophistication of its multi-cylinder oriental rivals but
it did have something that most of them lack, an almost human personality of
its own—idiosyncratic, occasionally unreliable but always
friendly.