Author Topic: B21 - So what exactly have I got here?  (Read 526 times)

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Group Leader

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B21 - So what exactly have I got here?
« on: 21 June, 2019, 16:24:16 »
Hi  Everyone,

Some may have spotted I joined the forum a few weeks back and today I have received my BSAOC welcome pack so now I'm a fully paid up member from  the Herts and Beds border.

I've recently acquired a 1939 B21 De luxe which is essentially complete (minus a speedo, see my previous thread) but needs a bit of TLC before it chugs off up the road.    It came with a BSAOC dating certificate that a PO had got along with an age related registration certificate.   It claims to be an Empire Star (by the badge on the tank) and on a previous MoT certificate although from my (very!) limited understanding of BSA model numbering I've not found any official reference to the B21 ever having that title.   I understand that the B21 was made between '37 & '39 and there was the complimentary B22 series which did have the Empire Star name.  It appears that a crude categorisation between the two models might be; the B21 series had a hand-change gearbox and the B22 had a foot-change box although it's not as a simple as that of course. 

My bike seems to be a bit of a hybrid (albeit matching frame and engine) as it is a B21 with a hand-change box adapted for foot-change with an external positive stop mechanism!   This mechanism wasn't working when I got the bike but I've now disassembled, cleaned, lubricated and correctly assembled it  (well at least better than it was) and now all four gears can be selected although you'd be stretching it if you said it was slick!  The mechanism seems to contain all the bits that would normally be found in the box and they look identical to the illustrations in various manuals of the foot change versions (Ratchet plate, 2 pawls, 2 parallel springs etc) so it looks like it was an official mod or upgrade.

From what I've seen there didn't seem to be a 1939 version of the B22 just the B21 standard and B21 de-luxe, so is it that the de-luxe is in essence the B22 / Empire Star or is it more likely that a PO stretched a point and applied Empire Star markings to it just to make it sound a bit more imposing?

I note in the members handbook it says that there are handbooks for the B21 and B22 series in the library but they do not appear in the member's area on the website (It does say on the website that Pre-War are not available) does this just mean they've not yet been uploaded but they could be acquired in the interim by more direct means?

Anyway, I'm sure they'll be loads more questions on girder forks, BSA head bolts, BSA colour schemes and numerous other topics over the following months!

Any advice / guidance gratefully received.

Thanks

Alan

« Last Edit: 21 June, 2019, 16:39:45 by Group Leader »

Group Leader

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Re: B21 - So what exactly have I got here?
« Reply #1 on: 21 June, 2019, 16:32:41 »
Here's the tank badge - is that original?

Oh, and the oil filter has had a bit of a makeover.

Alan

JulianS

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Re: B21 - So what exactly have I got here?
« Reply #2 on: 21 June, 2019, 17:36:26 »
Below from 1939 catalogue.

This was the year the 250cc C10 and C11 models were introduced.

Group Leader

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Re: B21 - So what exactly have I got here?
« Reply #3 on: 21 June, 2019, 21:05:46 »
Ah ha,  I see that the speedometer was an optional extra ;D  Shame the original purchaser didn't fork out for that option, still never mind!

But has anyone seen such an adaption of hand-change box to foot-change?   So far I've come across no refernces to the device or photographs of it.   And why did my B21 De-Luxe have a hand-change box anyway?   Maybe it was a subsequent replacement for an original foot-change that happened to be convienent (the tank doesn't have any fittings for the hand-change lever)? 

And is it an Empire Star or not?

Julian - In my B21 Speedo thread you kindly included an extract from the parts book.   Is that one of the documents that is available from the BSAOC library?

So many question for this BSA newbie!

Alan
« Last Edit: 21 June, 2019, 21:10:21 by Group Leader »

JulianS

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Re: B21 - So what exactly have I got here?
« Reply #4 on: 21 June, 2019, 22:40:08 »
No Empire Star models listed in 1939. Last ones were 1938.

I will send you a PM.

Group Leader

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Re: B21 - So what exactly have I got here?
« Reply #5 on: 12 August, 2019, 14:28:02 »
Carrying on the investigations into my B21 confirms, with the help of the information provided by various forumites here:
https://www.bsaownersclub.co.uk/bsaoc_forum/index.php?topic=5905.0

It does appears that the front hub is incorrect.   It has no facility for the speedo grive gear, the backplate is the wrong size, has an unusual aperture complete with mesh guard, a home fabricated torque arm but at least it does benefit from having some rather sporty cooling holes provided no doubt by a previous owner in a rather imprecise arrangement somewhere back in the mists of time.   

Nevertheless it's the only hub I've got and will have to do, at least for now!

The brake shoes have been re-lined by a local company for what I thought was a very reasonable tenner.   The backplate has been cleaned up by grit blasting and re-painting.    The brake drum looks to be in good order but a number of the wheel spokes are bent so they will need looking at.

Alan


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Re: B21 - So what exactly have I got here?
« Reply #6 on: 12 August, 2019, 14:44:39 »
As I mentioned in my other thread, I will need to contrive some sort of speedo.  This will be a home brew, electronic Chronometric job driven by a couple of magnets and a magnetic sensor housed in a dummy speedo gearbox (if anyone's got an appropriate, non-functioning but externally reasonable one please let me know!).  To that end, a brass ring has been turned that is a very good fit on the bearing housing into which a couple of rare earth magnets have been mounted.  The assembly has been loctited into position.

A complete Chrononmetric housing was purchased from a chap at the Banbury Run autojumble.   A prototype of the working bits has been assembled although there's still some software refinement to be done and the production version will have a higher quality needle drive actuator.   The wires from the wheel sensor will eventually pass up a speedo cable outer so as to look the part.  You can just see one of the magnets through the aperture and a temporary sensor mounting has been lashed up as you can see in the video.

Still the basic device seems to work and emulates, as intended, the operation of a proper job.

https://www.youtube.com/watch?v=4tPon8KCs74

Alan

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Re: B21 - So what exactly have I got here?
« Reply #7 on: 15 August, 2019, 21:10:36 »
Aha!  It seems that my B21 De -Luxe masquarading as an Empire Star with a funny front hub has got a Blue Star Gear change on it. 

I wonder if it's actually a Blue Star box too?   Pehaps I shall name it Bitsa.

You don't have to be Inspector Morse to work out what BSA you've got but it would certainly help!  :)

Alan

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Re: B21 - So what exactly have I got here?
« Reply #8 on: 04 September, 2019, 22:36:54 »
...... and an Amal 276 carb instead of a 275 and the main jet at 160 seems to be rather large for a 250 if I understand these things correctly.

Still, the primary cush drive has now been assembled so that the lobes properly engage with one and other (they were within an 1/8" of being disengaged when at rest when I got it).    The clutch which was locked solid with the retaining nut has been disassembled, thoroughly cleaned, re-assembled with hopefully the right clearance and, most importantly, locked in position with the tab washer (which hadn't been done previously).  Hey presto, you can actually disengage the clutch now so that's some sort of progress!

The carb has been completely stripped and cleaned, there was a significant amount of rust sitting in the bottom of the float bowl and all of the jets now appear to be clear.   On the mag; the points have been set and the timing checked, the HT slip ring cleaned and a decent HT cap installed. 

I think a random selection of cables had been picked up and thrown at the bike most of which were far too long and/or poorly installed.   Really most of them need replacing which I will do in slow time but they have been fettled to make them reasonably functional for now. 

Previously it has been very difficult to start, hard to keep running and even harder to start if it stopped.   Now after this "basic" maintenance at least it starts relatively easily and managed to keep running for 5+ minutes with no difficulty at all so hopefully we are moving in the right direction albeit slowly!


Hoppe30

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Re: B21 - So what exactly have I got here?
« Reply #9 on: 07 November, 2019, 15:58:08 »
Alan,

Having looked at your gearbox, it seems you have a 1920's gearbox with an early 1930's positive stop mechanism bolted to it. So it's not even a Blue Star gearbox. You need a B model gearbox. I have a fairly complete one which needs some minor repairs (clutch cable attachment is damaged). I am however looking for that positive stop mechanism that you have.

Kind regards,
Leon

BSA 1930s nut.

Trying to collect all 1936 models. Still missing B3, R17 and Y13.

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Re: B21 - So what exactly have I got here?
« Reply #10 on: 08 November, 2019, 17:00:32 »
Hi Leon,

I seem to have got the box/gear change combination working OK and I quite like the quirky combination of bits that form the bike as-is although I think it's quite a long way to how it was when it came out of the factory! 

So, I will concentrate on getting the bike back on the road and see how it goes before thinking about the possibility of changing the gearbox.   If and when I do decide to try and make it more "original" I'll let you know.

Cheers

Alan