(M21
specifications recorded. Click
here for M20 specifications)
Year
1937 - 61
Engine
Four stroke, single cylinder, side valve
Capacity
591 cc / 36.1 in
Bore x Stroke
Up to 1938: 85 x 105 mm
After 1938:
82 x 112 mm
Cooling System
Air cooled
Compression Ratio
5.0:1
Oil Capacity
2.4 L / 5 US pints
Carburetor
1937-38: Amal 76, 1939-45: Amal 276, 1945 onward: Amal
monobloc
Exhaust
Single, chrome
Induction
Aspirated
Ignition
Magdyno
Battery
12 V
Starting
Kick
Max Power
11 kW / 15 hp @ 4200 rpm
Clutch
Multi-plate, dry
Transmission
4-Speed
Final Drive
Chain
Frame
Twin cradle
Front Suspension
Up to 1947: Girder
After 1947:
Telefork
Rear Suspension
Up to 1947: None, spring loaded saddle
After 1947:
Plunger type
Front Brakes
Up to 1955: Drum, 7 in
After 1956:
Drum, 8 in
Rear Brakes
Drum, 7 in
Wheels
Steel, laced spokes
Front Tyre
3.25 x 19 in
Rear Tyre
3.50 x 19 in
Dimensions
Length:
2180 mm / 85.8 m
Width:
740 mm / 29.1 in
Dry Weight
167 kg / 369 lbs
Fuel Capacity
11.4 L / 3 US gal
.
BSA motorcycle combinations were the mainstay of the AA's breakdown fleet in the
1950s and the early 1960s. The AA used over 2000 of the M20, and later M21
models, and was the last purchaser of the M21 when production ended in 1961.
The M21 combination was an unsophisticated but robust machine, powered by a
600cc single-cylinder sidevalve engine producing a modest 15 bhp, which
propelled it to barely 50mph.
The AA ordered a different specification from standard, which included a
stronger front brake, a 12v alternator instead of a dynamo to power the two-way
radio, and higher, 'western-style' handlebars.
600cc single-cylinder sidevalve engine
600cc single-cylinder sidevalve engine
Various types of sidecar, leg-guards and fairing were produced.
During the 1960s the need to carry more equipment (not to mention the desire of
AA patrols to keep out of the weather) meant that the motorcycle combination was
gradually replaced by the Mini van. It was the end of an era – the traditional
AA patrol salute was abandoned in 1961, and the last BSA was retired in 1968.
There are 4 BSA M21s on the AA's heritage fleet, looked after by various AA
breakdown patrols around the country.
I'd never ridden a motorbike and sidecar before. 'There's
nothing to it,' grinned the cartoon artist Nick Ward cheerfully
- but then he would, wouldn't he, because a) he ran BSA M21
outfits as his primary transport for many years, and b) had sold
the test outfit to his neighbour Dave Watson. And as I got ready
for a first go on the BSA and sidecar, Nick and Dave were
exchanging looks with a gleeful edge not too far below the
surface. 'Nothing to it', hell -- I know I'm in for trouble.
The AA outfit in question was the earlier kind, with just a
plain box sidecar, not the 'plastic fantastic' streamlined
fibreglass type introduced from 1961-on. And this M21 bike
didn't have the later 12-volt, crankshaft-mounted alternator to
supplement its 6-volt Magdyno and help with the auxiliary
equipment, which by then included radios. It also didn't fit the
higher 'Western' handlebars with which these models were
catalogued, or the metal legshields often featured. But there
had been plenty of variations among the 2000-odd RSOs (Road
Service Outfits) during the Fifties, and it did have the fuller
front mudguard and Avon half-fairing; its 8 inch sls front brake
had by then been made standard on BSA's remaining big side-valve
slogger. There were no AA logos remaining on the tank or
fairing, but it was unmistakably ex-AA.
This engine proved an easy starter, and once fired up, the motor
also kept going with a wonderful steadiness, no matter what
Nervous-Nellihood it was subjected to. So - no more putting it
off -- here we go. Boot the gear lever up into first, let out
the clutch, and...
And why had I let them park it on that patch of shingle?! It was
like trying to drive off a pebbly beach. The rear wheel dug in
and spun, the sidecar wheel tried to overtake the bike, and for
the first time but far from the last, the Norfolk air turned
blue as I panicked. There was a deep gouge in the shingle by the
time we'd spat a lethal shower of stones backwards and lurched
onto the tarmac.
Where things were no better! Sidecar outfits wobble! In
desperation, before leaving home for this foolishness, I had
consulted my 40 year old copy of 'Teach Yourself Motor Cycling',
a little blue and yellow book which had served me well while I
was learning to ride. On the subject of sidecars, author Dudley
Noble (for it was he) observed briskly 'When first driving a
sidecar machine a rider naturally tries to balance himself... as
with his solo machine. The result is that the machine promptly
runs into the ditch...' Thanks, Dudley. 'It is only,' Dudders
continued, 'when the rider appreciates that he has got to
'drive' in similar fashion to driving a car, that he will steer
a straight course.' As a pal had put it, you had to treat the
handlebars as a steering wheel.
All right, all right, but meanwhile ... the sensation of lacking
control was genuinely terrifying! Either I or the infernal
machine, when braking or changing down, pulled hard to the
right, ie. straight out into where the oncoming traffic would
have been, if it hadn't been for that blessedly empty Norfolk
road. Expletives Deleted! A lot of them! Then coming to a halt
to re-group, I kept putting my feet down -- completely
unnecessarily, obviously, this was one bike that was not going
to topple over -- but down went the feet anyway, before the bike
had come to a halt, thus risking getting an ankle trapped and
torn in the tubework - but habit was too strong, you just
couldn't not. More expletives!
Underway again, the sidecar wheel was lifting, not on
left-handers, but just bouncing up on the inevitable bumps and
irregularities of a country road. This was, ah, unnerving, and
the bouncing of the springy saddle, counterpointing the minimal
movement from the bike's plunger rear suspension units, added to
the overall sensations of wibbly-wobbliness. Though it has to be
said that, once accustomed, this set-up did provide a
surprisingly comfortable ride. I motored down the road towards a
couple of cottages on a gentle right/left downhill bend, all
tensed up, which only added to my woes. But there were no real
problems - remembering some more advice from Dudley N, I
accelerated up to the right-hander then slowed around it, and
tried to motor round the left bend. The wheel stayed on the
deck. At 30! Hey, this was ... OK. So far...
Gently downhill for half a mile, and then there was a T-junction
with a busier road. Gingerly, slowly, and with my feet staying
firmly up on the rests, I turned the outfit round through 180
degrees and set off uphill again. Hey, that was definitely fun -
how often do you get to turn a bike on full lock with your feet
up? I negotiated the bends and throttled on a bit down the
straight - I was realising that things were better at 'speed'
than when attempting a slow cruise, or slowing down. In fact I
was feeling confident enough to try giving a twisted version of
the AA man's salute as I approached the others and began to pull
to a halt, changing down... AAARGH! BIG Expletive! As the
braking and gearchanging again sent us half way across the road,
from which the chaps prudently leapt for safety. When I did stop
it was a couple of hundred yards further on...
But I did another circuit, and another, cautiously growing in
confidence. This time down at the T-junction, doing my feet-up
turn with real enjoyment, an old boy in a modern Tonka Toy 4WD
lowered his window to stare, and then said 'Keep 'er going!'
encouragingly, though when I blurted out that it was my first
time on a combination, he accelerated rapidly away.
Owned
Conclusion
The final reckoning on the Sidecar Experience? Terrifying, but
do-able. I'd need a lot more practice before I felt OK in
traffic, because stopping was the most hair-raising thing. A
sidecar wheel brake, as found on, say, Panther's proprietary
chairs, might be a distinct advantage here.
But I did come to appreciate the pleasingly unified BSA outfit,
its unstoppable chugging poke; the details like the period
triangular-shaped handlebar grips which made life a lot easier
when you had to remove one hand from the bars; and particularly
the motor's sidecar gearing, which meant the power was always
there where you needed it - very welcome, and spot on for the
work. There was nothing to do about the lack of speed - I did
see 40, but 30 for the first time on the M21 outfit was more
exciting than 80 on a modern solo!
Article by Steve Wilson
Any corrections or more information on these motorcycles will be kindly appreciated.