BSA A10 Golden 650 Flash
BSA A10 Golden 650 Flash | |
Manufacturer | |
---|---|
Production | 1949 - 61 |
Engine | Four stroke, parallel twin cylinder, OHV |
Compression ratio | 7.2:1 |
Top Speed | 160 km/h / 100 mph |
Ignition | Lucas magdyno |
Battery | 6V |
Transmission | 4 Speed |
Frame | Welded seamless steel tubing with duplex downtubes and full cradle engine support, bolted-on rear sub frame |
Suspension | Front: Telescopic forks with coil spring - hydraulically damped Rear: None or Plunger-type, with shock and rebound springs, undamped. From 1954: Swinging arm |
Brakes | Front: Drum, 8 in. Rear: Drum, 7 in. |
Front Tire | 3.25 x 19 in., ribbed |
Rear Tire | 4.00 x 19 in. |
Wheelbase | 1391 mm / 54.75 in. |
Weight | 170 kg / 375 lbs (dry), |
Fuel Capacity | 16 L / 4.2 US gal |
Manuals | Service Manual |
It could reach a top speed of 160 km/h / 100 mph.
Engine[edit | edit source]
The engine was a Air cooled cooled Four stroke, parallel twin cylinder, OHV. The engine featured a 7.2:1 compression ratio.
Drive[edit | edit source]
Power was moderated via the Multi-plate with bult-in cush drive.
Chassis[edit | edit source]
It came with a 3.25 x 19 in., ribbed front tire and a 4.00 x 19 in. rear tire. Stopping was achieved via Drum, 8 in. in the front and a Drum, 7 in. in the rear. The front suspension was a Telescopic forks with coil spring - hydraulically damped while the rear was equipped with a None or Plunger-type, with shock and rebound springs, undamped. From 1954: Swinging arm. The A10 Golden 650 Flash was fitted with a 16 L / 4.2 US gal fuel tank. The bike weighed just 170 kg / 375 lbs. The wheelbase was 1391 mm / 54.75 in. long.
Photos[edit | edit source]
Overview[edit | edit source]
BSA Golden Flash (A10)
In May 1948, Hopwood joined BSA. Briefed specifically to create a competitive parallel-twin, the internally designated A10 model was based on an earlier A7 design by Page and Bert Perkins.[3] After BSA took over Triumph in 1951, Hopwood returned to Norton.
Early Golden Flash A10s had frames with either no rear suspension, or plungers, and had a semi-unit engine and gearbox, with the gearbox bolted to the rear of the engine.
Launched in October 1949, the A10 Golden Flash was a new post-war design, with most of the difference to the A7 being in the engine. Increased to 650 cc (40 cu in), it encompassed revised castings for the cylinder head and rocker box, and a cast-in carburetor manifold. The frame was available in rear rigid format, but the more common option was the then new plunger suspension, specifically designed for overseas export. BSA was a manufacturer who focused on machines for the working man, and so the design incorporated two practical use features: a hinged rear mudguard, designed to ease rear wheel removal; and a semi-unit engine and gearbox arrangement. The semi-unit power train enabled the primary chain to be adjusted via a slipper within the primary chain case.
The large carry over of parts from the A7 had the advantage of greater reliability, as it minimized the risk of any new technical problems. Launched in a new form of gold color, the combination of reliability and marketing made early exports possible, with 80% of production destined for the USA. The result was long delivery times for British customers, who were offered a more practical and less stand out black.
Although never designed as a fast machine, the Golden Flash was nonetheless fast for its time and competitive with the Triumph Tiger 100, achieving over 100 miles per hour (160 km/h) in tests in 1950, and covering a standing quarter mile (400 m) in under 16 seconds.[6] Its gold color also made it a marketing and sales success, out selling the red Speed Twin and the later blue-grey Triumph 6T Thunderbird, which was resultantly revised the following year into polychromatic blue.
However, BSA were concerned about a tendency for wear in the rear, plunger suspension, leading to uncertain handling. In 1954 it revised the model with a modern swinging arm, and the hinged mudguard was deleted. The semi-unit power train was also abandoned, making for a more involved procedure for adjustment of the primary chain, it offered benefits in the areas of the clutch and gearbox internals. The revisions also allowed for the launch of more sporting A10 Road Rocket.
In 1956, alloy brake drums were fitted as standard which both reduced unsprung weight and increased stopping power.
In 1957, the 40 bhp (30 kW) 105 miles per hour (169 km/h) BSA Super Rocket was launched for the 1958 season, with an Amal TT carburetor and high lift cam.
The final A10 development, and fastest in terms of power and performance, the 1962 BSA Rocket Gold Star, which fitted a tuned A10 Super Rocket engine into the well proven BSA Gold Star single frame. The result was a good handling fast bike that was a true classic. Current demand for the Rocket Gold Star, or "RGS", is such that non-RGS A10s are sometimes sold as originals, having been modified using suitable alternative parts.
With the launch of the new unit-construction (combined engine/gearbox) BSA A50 and BSA A65, the A7 and A10 were discontinued at the end of 1962 but the Rocket Gold Star continued into 1963 production.
Article from Two Wheels:
The BSA A10 650 twin, to give
it the most boring title in motorcycling history, may not be a
classic bike, says LESTER MORRIS (intent on beginning yet
another argument) but back in the early '50s it was a
state-of-the-art machine, solid as a rock, reliable as rain on
your holidays and today a mechanical relic that may well be
dragged screaming back onto the drawing boards because it used
so little fuel. But there's no questioning one thing: It was a
motorcycle in the Jbesr British tradition. . .
ASK ANYONE you know to name
the best-known British vertical twin, and they will say
"Triumph", and of course they would be right. It was popular
with enthusiasts and police alike, and it was a perfectly
acceptable motorcycle. But it was by no means the only true
British vertical twin BSA built a four-stroke vertical twin
which was at once similar in design philosophy to the Triumph
and yet very different in its basic specifications.
Initially a 500, the BSA grew
to 650 cub cm in late 1950 and retained this engine size through
design evolutions which saw Sports and Super-Sports versions and
finally, a new unit-construction model the A65 which appeared
in 1965. In the late '50s to very early '60s, the BSA Golden
Flash (even though later examples were painted black) was used
by the NSW Police Department as a sometime solo mount and a
frequent sidecar combination.
It was only the introduction
of the Mini-Minor which prompted the local police to abandon the
BSA and J.G. Murphy chair that little rollerskate of a car
rang the death-knell of motorcycling in general in the early
'60s.
The Golden Flash BSA is not
really a "Classic" motorcycle, but it certainly provides a prime
example of the state of the art of British twins of that period.
Like many of the machines which flourished then, this model is
currently almost extinct do you ever wonder where they all
went? but the few which are to be found are usually in
concours condition.
The subject of this
particular test, a 1953 model belonging to Col Brenchley, is all
that and more. In fact, thanks to modern baking and plating
techniques, the overall finish of the old Beeza is probably
better than it was when it was brand new! Understandably, the
gleaming and chrome-bright bike has won many awards.
From the inside
Typical of its era, the Gold Flash is powered by a long-stroke
pushrod-operated overhead-valve engine, with a primary drive by
duplex chain to a separate four-speed gearbox. The chain is
enclosed in an aluminum case on the machine's left side, with
the lower run of chain immersed in oil. The clutch, though
contained within the oil bath chaincase, is essentially a dry
component. Or damp might be a better word, which could be easily
proved by the incautious owner who would bring about instant
clutch-slip if he over-filled the case during service.
The BSA twin engine was
referred to as a semi-unit construction type because the gearbox
was bolted rigidly to the rear of the crankcases, instead of
being mounted separately behind the engine, like most of its
counterparts. Two bolts locked the gearbox to the rear of the
frame as well, the essential primary chain adjustment being
carried out by an external grubscrew which applied pressure to a
slipper-tensioner within the chaincase.
Naturally, unlike current designs, the gearbox carried its own
oil supply, as did the primary chaincase. In the dry sump engine
again unlike modern motorcycles the oil was carried in a
separate container attached to the frame under and at the back
of the fuel tank.
A single camshaft at the base
of the cast-iron cylinder barrel is driven by gear inside the
timing case, while the outer timing case contains the gear drive
for a twin magneto and a six-volt generator the latter driven
by a tiny 8x3 mm roller chain about half the size of the tiniest
overhead-camshaft drive chain.
The Gold Flash cylinder head is cast-iron, with an integrally
cast inlet manifold. A single carburetor is used; the pre-Monobloc
type with a fuel-raising "tickler" on the separate float bowl.
Sometimes an induction bias
occurred on BSA twins, with a slightly greater charge being fed
into one or the other of the cylinders probably due to an
unsquare mounting face which pointed the carby more towards one
pot than the other though there was a tapered anti-bias gasket
which you could fit to overcome this odd problem.
Apart from this quirk (which never manifested itself with any of
the other twins) this staunch British engine was a solid and
reliable mount which could cover prodigious distances without
much more than the simplest of routine maintenance.
The bottom half of the engine
was sturdy, with a bolted-up crankshaft and split connecting
rods with white-metal slipper bearings. A large ball bearing was
mounted on the drive side, while the more lightly-stressed
timing side was mounted in a large white-metal bush. This bush
needed to be replaced on occasion, even though it was fed the
first breath of fresh, clean oil from the gear-driven pump
mounted right alongside it.
An advantage of the semi-unit construction design, and the
basically simple overhead valve layout, lies in the ease with
which any reasonable owner can carry out servicing and large
repair jobs without removing the engine from the frame an
advantage not always enjoyed by owners of more complex, modern
motorcycles.
The power unit is bolted to a
duplex-down-tube frame with telescopic front forks and the dated
plunger rear suspension which, on this particular model, was
almost at the end of its run; the much better swingarm rear The
"ugly" side (at top) has the driveline. The large alloy case
contains the primary drive chain and clutch, while the counter-
I shaft sprocket on the gearbox mainshaft carries the final
drive from behind the clutch. Note the six-volt battery and
horn, ' both of which live in the open air. On the timing side
(above) the six-volt generator mounts in front of the crankcase
under the exhaust pipes, with the twin magneto behind the
cylinder base. The gearbox is remote from the power unit and is
driven by chain from the engine. Oil for the engine is carried
in the tank directly above the gearbox. suspension, in such
universal use today, was first adopted on the Golden Flash in
late 1953 as a precursor of what was left of the model's
production run.
A very neat nacelle contains
the simple speedo, lightswitch, ammeter combination which was
all one ever had or needed! on machines of that era.
Blinkers were not used, of course, though their great boon to
safety is currently unarguable, and most riders could manage to
find neutral gear without the aid of a little green light in
those days of yore!
Ups and downs
Plunger rear suspension was used on very many British machines
from the immediate pre-war era to the early '50s, even though
some makes notably Royal Enfield, AJS and Matchless ran
swingarm rear suspension on some models from 1949. The advantage
of the plungers is in keeping the drive chain in a constant
tension. Since little more than up-and-down movement is allowed,
chain tension remains reasonably constant.
The later swingarm suspension moves the wheel through an arc,
playing havoc with chain tensions (and life), though the extra
suspension movement and rigid wheel location allows greater
comfort and much better handling than plungers ever could.
On smooth road surfaces the
Golden Flash handles well and is comfortable enough, but the
limited travel of the rear suspension makes for a choppy ride
because of its undamped springs and the firm dualseat; arguably,
the plunger set-up was at its best when augmented by a single,
spring saddle to take the edge off bumps and potholes.
However, the machine does not
handle well by modern standards when ridden briskly over rough
surfaces and again this is due almost entirely to the rear
suspension. The axle is located within a pair of springs either
side of the frame and they can allow the rear wheel to get out
of whack with the front end when it moves through its 55 mm or
so of travel. This happens because the spring tensions or
frictional loadings may cause one side of the plunger system to
move further than the other, cocking the wheel to one side and
altering the geometry.
The bike will drop readily into corners, though the BSA
centrestand does not allow it to be dropped over too far. It
will track very securely, although a dip in the road or an
unexpected hole will catch the rear wheel on full bump,
resulting in a sharp tug at the handlebars.
I must say I had almost
forgotten this trick and it is only by making this sort of
comparison that one can see how much better the swingarm rear
set-up really is it is not yet perfect, but the pivoting-fork
suspension in current use is at least acceptable and allows safe
handling at most speeds this side of the ridiculous. By
contrast, the BSA front forks are excellent and certainly on a
par with the best in current use, but the old BSA trait of
heaviness at the steering head is still evident. It's hardly
serious, but the bike tends to teeter on the centre of the tire
tread when upright and at speed, which is a mite disconcerting.
Somebody once referred to this as the invisible cannonball
syndrome, as though a couple of these projectiles were attached
by ropes- to the steering head where they flop about
willy-nilly.
This syndrome is by no means
unknown to some of today's much vaunted motorcycles, in
particular the first Z1R Kawasaki models and the pre-1975 BMW
short-wheelbase 750s, so it may not qualify as a fault at
least not by direct comparison with machines which should not
suffer from this 100-years-old quirk!
Speaking of comparisons
between the old and new, for those of you who may find something
faintly familiar about the A10/BSA, might I draw your attention
to the first of the vertical-twin Kawasaki machines? Here is an
engine that is a dead-ringer for the pre-unit BSA, right down to
oil feeds to overhead rocker gear and the separate gearbox. A
copy, in fact, of the later Road Rocket sports model. At least
they had the decency to wait until the new engine appeared in
1965 but little attempt was made to disguise the origins of
the model. Though the engine differed in the bottom-end (notably
in the adoption of a ball bearing where the timing side main was
fitted) and a more bulbous timing case resulted, the castings
were almost identical and the general remarkably similar.
It's funny how you get used
to things, and it is only when you have to make do without them
that their great effectiveness is realised. It was never more
obvious than with the BSA, which has no mirrors! Mirrors were
not required 25 years and more ago, and neither were stoplights
or blinkers, as I've mentioned and the lack of them makes
riding in traffic a pretty nervous business. You can't tell who
is breathing down your neck, and you can't tell where they are
if they are!
Starting the bike took me
back to years ago, for the old Amal carburetor, with its
separate float bowl and fuel-raising "tickler", needed to be
flooded to provide juice for the long kick, and 325 cm3 of
cylinder is not as easy to punt over as it once was. Perhaps the
Golden Flash BSA is getting a bit old for that sort of thing.
Aren't we all!
The donk needed several kicks to bring it to life, and it idled
in the typically lumpy way of that period. Coming onto the
needle at about one third throttle and running there made for
some snatchiness, but this could be tuned out without too much
hassle if it annoyed; again reminiscent of the type of
carburetor which was used at that time.
Vibration was, of course,
part of the engine design, as it always was and always will be
in vertical twins. There is no way it could be described as
unpleasant. Rather was it a sign of an honest engine working at
its task, the essential changes of engine masses inevitably
resulting in transferring of shock loads to frame and rider.
There were some machines
which made a feature of heavy vibration, but the BSA twin, at
its best, was not one of these.
Modern motorcycle designers go to great pains to mask the
inherent vibration by building shafts which revolve in odd
directions, but the initial vibrations are still there, masked
by other vibrations which are said to cancel them out. Perhaps
it would have been nice to have enjoyed this feature on the
early British twins but it was apparently deemed unnecessary. Or
perhaps they didn't think of it.
In '71 the Flash came alive
again. This is Kawasaki's WS1 BSA copy. Enthusiasts of the day
said it didn't leak or vibrate as much as the Beeza. They were
wrong!
A bike of its time
The Golden Flash BSA is a perfect example of a mid-'50s
large-capacity British vertical twin, the type of machine
much-maligned by modern riders who have perhaps never seen one
of them, and almost certainly never ridden one.
It would be a surprise to
many to find out that the drum brakes are brilliant, the alloy-backplate
200 mm front one in particular. The wide shoes and quick-opening
cam certainly help, and so too does the bike's comparative light
weight. That front anchor is very powerful and progressive in
action, with little hand pressure required. The 175 mm rear drum
is equally efficient, and both brakes enjoy the priceless boon
of being just as effective in the rain as they are in the dry.
There are not too many modern motorcycles you can say that
about!
The virtues of the BSA twin
have been spelled out and so too have its vices, but it remains
a prime example to be stacked up against the models from Japan
with similar engine capacities, and of course against the
survivor . . . the Triumph Bonneville. It shows up well in
direct comparison, quite apart from its comparatively leisurely
performance (though it was quick enough in its day) it was dead
reliable, its handling and comfort were acceptable enough and
its fuel consumption was better then though we hardly knew it
at the time than many a 250 motorcycle today.
As a point of interest, the
test model leaked not a single drop of oil on test, and remained
in showroom condition throughout. With the accent very much on
fuel consumption as we head into the '80s you can't help but
wonder whether the large-capacity twins will once again appear
with low compression pistons, single carburetor, "soft"
camshafts, small valves and modest power outputs.
And if they do which seems
more and more likely how well would the old BSA then stack up
against its modern counterparts?
Quite apart from its rear suspension, it would come through very
well, very well indeed.
Source Two Wheels 1981
Make Model | BSA Golden Flash |
---|---|
Year | 1949 - 61 |
Engine Type | Four stroke, parallel twin cylinder, OHV |
Displacement | 646 cc / 39.4 cub in. |
Bore X Stroke | 70 x 84 mm |
Carburetor | Amal |
Cooling System | Air cooled |
Compression | 7.2:1 |
Lubrication | Dry sump |
Exhaust | Twin, stainless steel |
Ignition | Lucas magdyno |
Battery | 6V |
Starting | Kick start |
Max Power | 26 kW / 35 hp @ 4500 rpm |
Clutch | Multi-plate with bult-in cush drive |
Transmission | 4 Speed |
Final Drive | Chain |
Gear Ratio | 1st 11.68 / 2nd 7.96 / 3rd 5.48 / 4th 4.53:1 |
Frame | Welded seamless steel tubing with duplex downtubes and full cradle engine support, bolted-on rear sub frame |
Front Suspension | Telescopic forks with coil spring - hydraulically damped |
Rear Suspension | None or Plunger-type, with shock and rebound springs, undamped. From 1954: Swinging arm |
Front Brakes | Drum, 8 in. |
Rear Brakes | Drum, 7 in. |
Wheels | Steel, wire spokes |
Front Tire | 3.25 x 19 in., ribbed |
Rear Tire | 4.00 x 19 in. |
Dimensions | Length: 2100 mm / 84.0 in. |
Wheelbase | 1391 mm / 54.75 in. |
Dry Weight | 170 kg / 375 lbs |
Fuel Capacity | 16 L / 4.2 US gal |
Top Speed | 160 km/h / 100 mph |
Standing Quarter Mile (400 M) | 16 sec. |
Colours | All over gold, Black/chrome |
Source | Wikipedia, Two Wheels Magazine |