650cc Thunderbolt Review
Illustrated November 1967
Fancy something different? Tired of the same
old journeys to the coast, stuck in traffic
jams, burning the clutch? Then treat yourself
to an Ordnance Survey map, costing only a few
shillings from H.M. Stationery Office. And a
BSA Thunderbolt. It's unlikely you would get
a Thunderbolt from the HMSO, but a visit to
your local showroom is well worth while. As
a combination, a good map and a fine bike will
recapture the "good old days" of motorcycling
when the restrictions were few and the
So, armed with some HMSO sheets, I filled the
four-gallon petrol tank of the big BSA on loan
from the factory, and we despatched ourselves
early one cold morning in a westerly direction.
The Thunderbolt, as you probably know, is the
single-carburetter version of the twin-cylinder
654 cc BSA range, made with the sidecar man
in mind. But there are those who, with no intentions
of ever adding another wheel, prefer a single-carb
machine. Not so fickle, nor do you have to worry
about synchronisation. And performance differential
is hardly worth (Mentioning, particularly in
'these speed-conscious days.
Despite its re-styling, I still found the Thunderbolt
reminiscent of the old Gold Flash. If you
have a successful basic formula, why bother
to change it?
The 75 mm by 74 mm engine is identical, but
for cams and compression ratio, to that of the
quicker 654 cc machines. While the Spitfire
Mk III, the Hornet and the Wasp have a 10.5:
1 or, the Thunderbolt—and the Lightning,
surprisingly— has 9.0:1. Gear ratios of
the Lightning, Thunderbolt and Spitfire are
identical, each having a 20 tooth gearbox sprocket,
a 47 tooth rearnwheel sprocket and a 4.87 :
1 top gear. So, despite the reputation—and
a well-earned one—of the siports models,
the Thunderbolt would never be far 'behind.
They're a handsome bunch, too. Sit astride,
and you'll find yourself looking down at a chromium-plated
headlamp embracing the lighting switch
and ammeter, and a conventional handlebar
layout. Dip-switch and horn button are incorporated
in the left-hand grip. On this model, there
is no tachometer, and the 150 mph speedometer
is rubber-mounted at ithe top of the left fork-leg.
Gearchange lever readily adjustable and rear
brake lever are comfortably situated, but I
wouldn't say that this was 'the most comfortable
machine I had ever ridden. The petrol tank tends
to 'be bulky, rather than sleek, forcing one's
knees rather far apart. And I found the suspension,
both front and rear, to be hard, giving, after
a long trip, a jarring ride. This, no doubt,
was due to the heavier springing provided for
use with a sidecar, tout gave the impression
of a progressively-hardening saddle.
Roadholding is excellent. For a big bike, weighing
391 Ib, it could be cornered with .the utmost
confidence, in both wet and dry road conditions.
Braking was to match, particularly the
8-dn front unit, which could always be relied
upon to retard one's progress as rapidly as
was mechanically possible.
Petrol consumption varied from as little as
an approximate 42 mpg during a motorway thrashing
to as much as 65 mpg on my day's outing. And
it isn't necessary to buy the Super-Extra fuel—the
Thunderbolt is happiest drinking the four-star
stuff through its 1-J-in Monobloc carburetter.
Lighting is, as may be expected, well up to
scratch, the headlamp always providing sufficient
power, in keeping with road-speed at eight.
The horn had a strangely muted sound, but was
always sufficient warning for other road-users.
So, as I said, we were all set for an interesting
day, having decided on a route following Roman
roads, many of which laid the foundations for
our modern trunk roads and motorways.
If you're a prize chrysanthemum grower or dahlia-fancier,
and you would like a little heaven-sent rain
to freshen-up your li.ttle .treasures, drop
me a line. I couldn't really be accused of being
a "fair-weather" motorcyclist because,
with only one exception in the past twelve months,
it has rained during each of my road-tests.
Not just rained. The sort of stuff that, if
Noah was still around, would send him rushing
to the do-it-yourself shop with an open cheque
and an order for 15 cwt. of six-inch nails.
Not that I mind a little rain. It's a lot of
it that I object to.
It was a (need I say it?) dark, wet morning
when I ruddy awoke the Thunderbolt from its
dreams of high-speed cruising alomg sunbaked
highways and started its big engine with a solitary
prod of .the kick-starter, and a half-dosed
air slide The key to the coil-ignition system
is situated on the left of •the steering
We splashed our way through the streets of
London which, at .that hour, seem only to be
used by car-loads of burly men wearing concrete-impregnated
jackets and Wellington boots. with a 10-inch
Leaving London (Londinium to the Romans), we
left via the Chiswick roundabout and Kew to
Stanwell and thence down one of England's oldest
roads, the A30, to Staines (Pontes).
In traffic, you would never imagine that it
was a 650 on which you were sneaking through,
except when the throttle is opened and the acceleration
.gives a sharp reminder.
From Staines, we continued along A30 past Basingstoke.
after which we forked right on A303 to Andover,
cruising at a steady 60-65 mph, despite diabolical
weather, and ducking beneath great clouds of
spray thrown up by west-bound lorries.
Through Andover, out on the A303 past Weyhill
(and Thruxton), then off to the left and the
old city of Salisbury, lording it over its Plain.
Picking up the A30 again to Shaftesbury, we
passed through Sherborne and across the county
'border into Somerset and Yeovil, where a right
turn will take you up the Roman road to Ilchester
(Ischalis). This route rarely follows the line
of the Roman road, which ran from Staines to
Silchester (Cal-leva), 'but is its approximate
And now one is on Fosse Way, truly one of Britain's
oldest roads, up on A429 to Stow-on-the-Wold,
Moreton-in-Marsh, crossing in an almost straight
line the A34. Through the village of Halford,
and in a quarter of a mile or so the A429 bears
left for Warwick.
In about 200 yards, the B4451 bears right and
a lane goes straight ahead. This is the Fosse
Way proper, and taking it ft like going 'back
into history. Almost straight as a die, it carries
on for almost 30 miles to become B4029 just
Turn right here, and you are back in 1967,
on a modern motorcycle, and it's still pouring
with rain. Down the A5, passing Towcester (Lactodorum),
and along this fine Roman road brings you back
into North London.
There you are. If you want an unusual day out,
try this route. And if you want superb motorcycling,
try a BSA Thunderbolt.
But don't go on the same day as me. Unless
you're a flower-grower, of course.