The BSA B21 on the other hand; is of a recognisably traditional style: the frame and forks are of a type fitted to many of the BSA range: the Engine and Gear-box are of the pre-unit style; and looks like an early B31, Ariel or Triumph single of the period; thanks to Val Page. The Primary chain-case; from pressed steel, you can find on any BSA. From 1936. Till 1950. It runs off a Lucas Mag-Dyno, like almost every other Bike of the era; the control levers are pressed steel and the Advance-Retard and Choke controls are of the more regular “Amal” type.

This machine came to me when the father of a friend, decided to emigrate to Cyprus in 2002 and sold me his project; which consisted of roughly 60 % of the bike; which was totally dismantled and scattered all over his garage after an attempted burglary. This restoration required much searching for the correct parts; hence, it took two and a half years of my busy schedule:

Compared to the New Imperial, the BSA, is a “Big “Bike; there’s lots of room for the rider; it feels long and heavy.

To start this one; the ignition is turned on with a small switch on the seat tube; the conventional Amal “Mazac” carburettor flooded and the choke left open, then the Engine shows that it has lots of Flywheel effect, as it just rolls over and starts with more reserve than the New Imp, then settles into a steady idle: this engine has rather more conservative cylinder dimensions, of 63x80. And the performance reflects this.

The gear-change, 4.speed, 1st down and 2.3.&4. Up, is noisy and needs much concentration to change quickly. The handling is slow to the point of being ponderous and feels like it’s hinged in the middle, not inspiring confidence in the turns; the brakes are quite good; but there are frequent times, when you find that you are holding the throttle wide open, without realising it. Don’t get me wrong; this is also a very good bike to ride for a long distance; and it too will cruise all day at 50. MPH. But not quite so well on the hills. It just takes a slightly different mind-set; or maybe just patience.

There are inevitably some small deviations from standard on these Machines; just to make them more usable; for which, I hope I am forgiven: The dynamo on the New Imp, is fitted with a solid state Regulator; C.Wylde and Sons of Leeds. Instead of the old three brush system, which never really worked; even so the Dynamo output is so small, that you cannot use the Headlamp; unless travelling at very high revs: So I have fitted an LED bulb, (Classic Dynamo and Regulator Conversions). which consumes much less current and so lets me see where I’m going.

The Magneto, on the BSA, failed on the first outing and caused much frustration; so I set myself the task: To convert it to coil ignition, without any change of appearance from the outside: This was done, by removing the Magneto armature and fitting a Tiger Cub “Distributor” in its place: this involved making a new shaft, to accommodate the Dynamo drive gear and changing the direction of the Advance Mechanism: So it now has points ignition and Auto Advance; All fitted inside the Magneto casing, (hence the ignition switch) and you can still get to the points through the usual end cap. This system is OK because the Dynamo has sufficient power, to supply conventional lights and still uses the original Cut-out Regulator.


It’s the simple things in life which make restoring a bike such fun; like the conversation I had with the sales person at “Armours”, when I called them to enquire about an exhaust for the BSA: the conversation went something like this;
“Q” could you supply an exhaust system for a 1938 BSA,B 21.?---“A” Aye lad; is it side-valve or OHV ? –Its OHV.--- “Q” is it a ---Yes it is: Is it Foot or hand change ? ---. 4 speed hand-change: “Q” is it 1- 3/8” at the exhaust port ? Yes it is:
In that case, we can supply one off the shelf:---

It’s my turn to ask questions now: can I have an option of Barrel or Fishtail silencer ? Aye lad:--- well I would like a fish-tail with clamps if possible: Aye lad, just give me your credit card details and it will be in the post: and it was.

What an entertaining way to order parts, from a good old fashioned firm like that. So it is easy to see, that my “twins”; although made in the same area and in the same year; are like Chalk and Cheese and give one a great variety of riding experiences, good reliability and lots of fun: With a family wish for good measure: Great partners in any stable; and here to stay.

John Wood 2016.

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