We all do strange things at times. There I was riding a fast(?), reliable GS550 and then for no logical reason, other than the fact that all my mates ride old British Iron, I sold the Suzi and bought a BSA A10. And from a dealer!
It must have been a pretty bad attack of irrational behaviour. After horrific expense, the A10 was on the road and as reliable as 30 year old vertical twins come. Good.
Except that when I tried riding it to work, the iron motor would emit an embarrassing amount of smoke as the inevitable oil leaking past the rocker box gasket (read brown paper) was cremated. A few minutes later, the head would reach incandescence and defy the efforts of the carb at vaporising petrol until the bike had cooled for a while. Didn’t they have traffic jams in 1955?
Anyway, after a few attacks of the vapours (not me, the A10), I became pissed off and instead of doing the logical thing and selling the bike pronto, I decided to get a small bike for work and save the 650 for weekend bashes with the local idiots in the classic bike clubs. What would you have done. Bought a C90 or a GP100?
Well, I didn’t, I acquired a ’68 BSA Bantam Supreme (no worse than Super Dream as a stupid name). "Just needs a battery, mate, and a back tyre and she’ll be as good as new..." Well, at least it was cheap and on the Swansea Megabrain. Once I found a battery and new kickstart (and shaft), I attempted to start it. No go. The wiring had been assaulted by an electrophobic moron who’d thrown most of it away.
Not for nothing was I trained as an electronics engineer, though, so I soon had the loom re-jigged and even managed to get the motor running. All it needed, after that, was a new small end and a head with some spark plug thread I'd‘be on the road. Oh, there was the little matter of the swinging arm bearings and I did have to recover the seat and replace the back wheel and buy a new rectifier and brake linings and a speedo drive gearbox and various bulbs and a new set of tyres and...
Anyone who’s done this kind of thing can complete the list. At least spares are cheap compared to Jap ones, and easy to find considering the factory was pulled down in 1974. Eventually, I rode it round to the MOT man and got a bit of green paper.
So my Bantam riding days began, belatedly at the age of 36, perhaps, and without my wife, who refuses the pillion seat at all costs. The 175cc 2-stroke single isn’t nearly as bad as some of those Villiers monstrosities specified by most British lightweight factories (why? - because they were ludicrously cheap, of course).
But then, the Bantam engine was nicked from the Krauts in 1945. By 1968 the original DKW 4.5hp motor had acquired a bit of poke, with a claimed 13hp from a 10:1 compression ratio, but it still ain’t going to worry most Jap 125s.
And, wonders of wonders, there’s actually a four speed box, which is absolutely essential because the power band is narrower than a Honda 50 back tyre. You can coax the vibrating, smoking, D14 up to an indicated seventy on a flat road — if you’ve got a back up vehicle following to pick up the footrests, side panels and bits of battery. Cruising speed is more like fifty, though, if you want the motor to outlast the rear chain - at this sort of pace it does a hundred to the gallon.
A week after the triumphant MOT pass, the bike died suddenly. We electronic buffs know a flat battery when we see one, this one resembled a hedgehog on the M1. When I got it home (fortunately they are easy to push), I found the Wipac alternator windings were black and the battery had boiled. Foiled again!
The crude (and, of course, cheap) battery charging circuit fitted by Mr BSA to their cheapest of Beezas relied on the incredible inefficiency of the crappy selenium rectifier to limit charging currents. Using a modern silicon device results in current beyond the wildest dreams of either the alternator or battery designer.
I bought a new stator (all the secondhand ones were charred - surprise, surprise) and rewired the bike with a 6.2 volt zener diode, taking the opportunity, while I was at it, to switch the battery out of the circuit entirely except when the headlight is on, You need a big capacitor, but it seems to have improved the notorious Bantam starting.
Back on the road again, much poorer, I had the opportunity to savour the excellent handling, the adequate brakes and the appalling lights. Maybe I should have converted to 12V while I was trying to rectify (sorry) the diabolical battery charging problem.
The bike’s not too bad in modern traffic conditions, though it doesn’t feel so much like a sixties bike as one from the fifties, but you can sometimes catch a learner on a restricted 125 unawares. You have to have the motor well on the boil to do that, it’s only a basic 3-port design with no reed or disc valves or electronic ignition, so torque is negligible outside the power band. The best hope is to come up behind a Jap bike with knackered shocks on a twisty road, then you can give the bike full stick and rely on the marvellous cornering abilities.
On the maintenance side, decokes and ignition timing are dead easy, just about everything else is diabolical. Never take the tank off - you need four arms to get it on again. The seat is supported at the back on the threads of the rear suspension bolts. It takes forever to get the back wheel off and even longer,to get it back on.
If you see a Bantam without oil on the front forks, it’s either just had it wiped off for the MOT or the owner has given up putting any in; it doesn’t make much difference to fork action and removing the top nuts requires a special socket.
The clutch is held together by a giant circlip which is a cinch to remove if you don’t mind clutch bits all over the garage, but is a pig to get back on again without the special tool. And so on. Oh, and the frame is in two halves which are bolted (yuk) together at the main electrical earth.
If you’ve a terrible desire to own a British hack with traditional virtues of good handling, crap electrics and mediocre performance, Bantams have the virtue of being cheap and uncollectable. Unless you’re a certifiable chauvinist on L plates, you’d do better to avoid the 125, which has no proper crankshaft lubrication and even worse electrics than the later 175s.
With the 4-speed bikes, look for an engine number beginning D14B or the crank will start knocking pretty rapidly. D10s are real turkeys and the B175 was okay. But I can’t think of any sane reason for not buying a used H100 or GP125 instead, unless you want to find out, at first hand, why the whole sub 250cc market defected to the Japs in the 60s.
Chris Washington