The 1971 Triumph Bonneville was the problem child of
a shotgun marriage. It was responsible for Triumph missing that year’s U.S.
sales season, and it just about bankrupted the company.
The late Sixties Triumph Bonnevilles were, and still are, considered to be the
best of the lot. But a major program of standardization was underway across the
BSA Group, which also owned Triumph. For the 1971 season, BSA planned to use a
new oil-bearing frame for both BSA and Triumph 650 twins.
However, the new Triumph frame had been designed around the BSA 650 engine, and
when the first batches of frames were delivered to Triumph’s Meriden factory,
assembly line workers found they couldn’t fit the Triumph engine in the frame
without removing the rocker boxes from the cylinder head first.
The 1971 Bonnies were already behind schedule because of production delays
caused by a shortage of parts - the result of teething troubles with a new
computer system. The cumulative result was that very few Bonnevilles were at
U.S. dealers for the critical April to June sales season. Other problems with
the 1971 bike included a seat height only suitable for people over 6 feet tall,
major frame failures caused by the center stand being mounted on the oil-bearing
“sump,” and aesthetics only a short-sighted mother could love. The 1971 model is
perhaps the least popular of all Bonnies.
Review
AH, THE BONNEVILLE. It has long
been a status symbol with the road rider. Not the same way as with other
big-bore machines. A BMW, for example, connotes Engineering, with a capital
E. An FLH connotes yet another feeling, that of bigness, luxuriousness, and
is the most unabashed symbol of affluent arrival.
The Bonneville symbol is a more
dynamic thing. If you are a sporting sort of rider, and deem yourself a bit
of a jockey, you may buy yourself a stable of intermediate machines with
good performance and handling, but you know you're waiting for the day you
can buy your Bonnie.
Its image does not jibe with the purist. The Bonneville is more for the guy
who would buy a Boss Mustang or a Z28. Performance-plus, flashiness in a
moderate way, and a respectable handling. Like the Sportster, the Bonneville
is a stud bike, although the two images aren't quite the same. But, in
either case, purchase of one or the other indicates "arrival," the coming of
the real motorcyclist, and real motorcycling.
It seems highly unlikely that
the designers of the Triumph Big Twin had this image concept in mind when
they created the basis for what was to become the Bonneville. That type of
marketing acumen didn't exist in the late Thirties. One can only conclude
that Triumph really lucked out, because the half-stud, half-racing
"Bonneville image" is the very thing that has kept that firm alive and well
to this date.
THE ANCESTRAL SPEED TWIN Triumph's 1938 Speed Twin 500 heralded what was to become the most popular
design, and the most plentiful motorcycle of that design, to ever come out
of England. The alternately firing, vertical twin-cylinder engine produced
28.5 bhp, and, with a machine weight of 365 lb., provided the sporting
enthusiast with an ideal mount. In fact, the 1939 sports version, the Tiger
100, became a popular machine with motorcycle connoisseurs. It featured an
individually built, dynamometer-tested engine producing 34 bhp, and had many
other "racing-type" features.
1950 was the year of the first Triumph 650 Twin, the Thunderbird. It had a
bore/stroke of 71 by 82mm, measurements which still hold today.
These husky machines rapidly
gained popularity in America, and became favorites with sports minded
riders. TT racing proved to be its forte and a look at the record books will
probably reveal that more races of this type have been won by 650 Triumphs
than any other single machine.
The first Thunderbirds had a
sprung hub rear suspension system which consisted of a huge rear hub with
springs inside that provided a couple of inches of travel. It rode better
than a rigid frame, but the hubs were heavy, had no dampening
characteristics, and were prone to bearing failures.
This form of rear suspension was
employed on some of Triumph's models imtil 1954. when a swinging arm frame
appeared.
Along with the frame came the new T-110 model, a super-sports version of the
Thunderbird. It featured an alloy cylinder head with large valves, high
compression pistons and a sports camshaft.
At that time, they were about
the fastest road bikes around.
Several other 650 models appeared in the ensuing years, including the
popular Trophy and TT versions. In fact, until the "Japanese Invasion," big
Triumphs were
the most popular machines around in most parts of the country.
A REVAMPED PACKAGE
For 1971, Triumph has revamped practically everything on the 650s except the
engine/gearbox package, and even a new five-speed gearbox is optional. Still
functionally British in appearance, Triumphs have sprouted many modern-day
innovations and styling trends. Gone are the familiar front forks and rear
wheel hub. Turn signals are now standard equipment, and gracefully tapered
silencers with a gradual upsweep adorn the Bonneville. Large, conical wheel
hubs housing improved brakes, and a wide dual seat improves rider comfort.
Perhaps the most interesting
aspect of the new 650 is the frame. Twin tubes extend from the steering head
below the engine, and then up to the top rear suspension mounts. A large
diameter central tube holds 3.5 qt. of oil, which does away with the old,
separate oil tank. The "spine's" larger size makes for a stronger frame. The
engine is firmly bolted directly to the frame at the front and underneath,
and steel plates support it at the rear.
A flat support anchors it on
top. Gusseting at the front of the swinging arm, which pivots on bronze
bushes, appears very beefy, but the tubes themselves look rather delicate.
Welds are very smooth, and the paint is excellent.
Steering geometry felt just right for normal road riding, with a bit of fast
swervery thrown in. Gone is the tendency of earlier Bonnevilles towards
understeering; in fact, the new Bonnie feels rather like its little brother,
the Triumph T-100 500-cc Twin, which is several pounds lighter.
The installation of a 3.25-19
Dunlop K70 tire seems to be the trend these days, and it probably helps
smooth out the bumps a little, too. Traction is very good, with no tendency
towards side-slipping at low speeds.
ROLLER BEARING STEERING HEAD Part of the Bonnie's hairline steering and good ride are attributable to the
new front fork assembly, which rides in tapered roller bearings. The fork
legs feature cast alloy sliders with rubber wipers and internal springs.
Full two-way hydraulic dampening and almost 7 in. of fork travel help make
them one of the best operating fork assemblies available. Even with two
aboard, no bottoming occurs, and there is no annoying clank when they topped
out going across railroad tracks or badly surfaced roads.
The rear suspension units are,
of course, Girlings, and aside from seeming to have a slightly stiffer
spring rate than earlier Bonnevilles, they added immeasurably to the
handling and ride. The chrome plated springs are a nice touch, but the
damper rods are left exposed, which could cause premature wear of the seals
if the machine is ridden in wet or dusty surroundings.
The wheel hubs are very racy in appearance and house an excellent set of
brakes. Diameter of the front unit is 8 in. It has twin leading shoes. The
pivot arms are pulled toward each other like a BMW and therefore no
equalizing rod is used.
A functional airscoop funnels cool air into the drum and carries off excess
heat and brake dust. Even after several hard, high speed applications, the
front wheel continued to do its share of stopping the machine. The rear
wheel is similar in appearance, but the brake drum is an inch smaller in
diameter. Although less positive in feel than the front brake, the rear was
smooth in operation.
In addition, the rear sprocket
may be unbolted for easy gear ratio changes or replacement. One point we
don't care for is the rear wheel speedometer drive. It necessitates a long
cable, and is less accurate than a speedometer driven from the front wheel.
A FAMILIAR ENGINE
Basically unchanged from last year, the Triumph 650 engine remains one of
the Western world's mechanical marvels. It starts easily, vibrates only
mildly, and has good power available throughout a wide rpm range. Both ball
and roller bearings support the ends of the crankshaft; plain insert rod
bearings and wrist pin bearings provide quiet running and high load carrying
capability, and 9:1 compression ratio three-ring pistons take advantage of
today's high octane fuels.
A separate camshaft for the
intake and exhaust valves makes it possible to have pushrods of equal
length, and makes it easy to degree-in the camshafts for optimum
performance. Both shafts are gear driven from the crankshaft and ride in
sintered bronze bushings. The double-plunger-type oil pump is driven from
the inlet shaft, as is the crankcase breather, and the exhaust shaft drives
the contact breaker assembly.
A welcome change to the 1971
650s is the addition of four inspection. caps on the sides of the rocker
boxes. When these caps are removed, a feeler gauge can be inserted to check
the valve clearances. This makes it easier to obtain really accurate valve
clearance settings.
Twin 30-mm Amal concentric carburetors breathe through "tuned" intake tubes
which terminate into gauze air filter elements. These are housed in metal
boxes under the seat and are very clean looking and stylish.
Although the carburetors are
fitted with choke slides, we didn't find it necessary to close the lever
even on cold mornings. Just make sure the float bowls are liberally primed,
the ignition switch is on, and most often the bike will come to life with,
at most, two kicks.
A twin-row primary chain is retained to drive the clutch. Adjustment is
accomplished via a rubber-faced tension slipper blade under the lower run of
the chain. Rubber inserts inside the clutch hub cushion the engine's power
impulses and increase the life of the chains and gearbox components. As
always, the Triumph's three-spring clutch was easy to operate and didn't
slip or drag.
HOW THE GEARBOX WORKS The Triumph gearbox shifts smoothly and is silent in operation. Shifting is
accomplished by a spindle and plunger assembly which pivots a quadrant that
in turn moves the cam plate. A spring-loaded index plunger fits into notches
in the cam plate for each gear and for neutral. Robust is the keyword;
essentially the same gearbox is used in the more powerful 750-cc
three-cylinder Trident.
Announced as an optional extra
is a five-speed gearbox with a slightly lower first gear, and the rest of
the gear ratios closer together. If it shifts as well as the four-speed
gearbox, it'll be a winner.
Due to the incorporation of the
engine oil into the frame, with the resulting large main tube, the gas tank
is now slightly bulbous in the front section in order to keep the area
between the rider's knees down to a reasonable width and retain the 3.5 gal.
capacity. The seat, although very comfortable, is quite high at 34.5 in. Two
of our shorter staffers found it impossible to plant both feet squarely on
the ground. Another point that vexed us slightly was the unsightly oil
pressure indicator sender unit which protrudes from the right side of the
crankcase and is covered with an ugly rubber cap.
The indicator light is located
in a spot (on the back of the headlight shell) which makes it difficult to
see when illuminated, except at night. Oil system failures on the large
Triumphs are so rare these days, it seems that the indicator could have been
left off.
RUBBER-MOUNTED INSTRUMENTS Rubber is used to mount the handlebars to reduce vibration, and the
new-style Smith tachometer and speedometer nestle in their own isolation
mounts. Both are quite accurate, but it's beyond us why so many
manufacturers (and the Japanese, too) insist on fitting 150-mph speedometers
on machines that won't pass the 120-mph mark. Besides being superfluous, the
numbers
must be made smaller (or fewer must be used) to keep them from being too
small to read comfortably.
Another sore point, which we
recently found on another British machine, was the new, improved Lucas
electrical control units/lever holders. These cast aluminum units are very
dull in appearance and have sharp plastic blades which must be flicked up or
down to operate the turn signals or dip the headlamp. These blades are
sharp, of a peculiar shape, and look as though they'd be easy to break off.
Two buttons, one above and one below the blade switch, operate the horn and
high beam flasher on the left; one button on the right is an engine cutout
and the other button is left free for some other function.
The remainder of the electrical
system deserves praise. The headlight throws a wide, powerful beam, the horn
is suitably loud in volume, and the wiring is very well done. Triumph has
taken great pains to rubber-mount the coils, rectifier and battery, and the
area under the seat is used to its best advantage to locate these items for
easy access. A new four-position ignition and light switch allows the rider
to leave his machine parked with the ignition locked off and the parking
lights locked on at the same time.
Other nice touches are
rubber-mounted front fender braces, the overall excellent quality of finish
(both paint and chrome), and precise handling qualities. This machine is one
of Triumph's best.