BTH Magneto for 1930 Scott TT Rep

[Orgasmatron]

Further to my recent posts (nobody answers mine either Brian – it seams that nobody is interested in 2″ dia LHS exhausts at the moment), I have come to the conclusion that a 1930 TT Rep would have been fitted with a BTH M2 magneto, if it didn’t come with lights (unless anyone can tell me differently). Some people have suggested BTH MC2, but these appear to be manufactured slightly later.
However, M2 or MC2 would anyone know if it should be the small taper female thread version or the large taper male thread version.
Chris.

[BRIAN MARSHALL]

Hi Chris, Carl Storm in Norway will probably be able to give you ‘chapter and verse’ on this subject, but if you ever get the chance, I would urge you to have a look at the factory records in the VMCC library as they detail such things, and even give the individual serial number of the magneto fitted to each bike ! As with all things Scott, what they fitted depended on how much credit they had with the supplier, AND what the customer wanted, plus whether or not the bike was ordered with a lighting set. So… You could get BTH or Lucas Magdynos/Dynamags, ( strictly speaking ‘Magdyno’ is ONLY a Lucas product ), as well as just a magneto on it’s own. ‘K-type’ BTH magnetos were also used on some TT Reps, but not as far as I am aware, on Flying Squirrels. These stand quite a bit taller than the ‘M’ series magnetos, and there is very little clearance if a chain-oiler tank is also fitted !
Very occasionally, Bosch magnetos appear in the records, then later in the 1930’s, Miller products begin to appear. I don’t really know the significance of the two different tapers, but the smaller taper, where the sprocket is retained by a bolt, is normally associated with the Super Squirrel (2 and 3 speed), whilst the larger taper, with the sprocket retained by a nut, is associated with Flying Squirrels and TT Reps, but don’t lose any sleep over that particular issue !! I hope this helps.
Brian

[chstorm]

Hi Chris,

On my 1930 TT replica there is a BTH magneto marked TT on top. On the lower part of the side of the magneto body, the following is stamped in:

BTH (logo) TYPE Kcv50 A1
No 1F 307922
MADE IN ENGLAND

I presume that the magneto therefore is a Type Kcv50 (Whatever that means). It is a very good magneto.
Photos are available, but I have not yet mastered the art of putting them on to the SOC forum. I can send them by e-mail if you so wish.

Kind regards,

Carl

[BRIAN MARSHALL]

That ’50’ number in Carl’s magneto type suggests to me that it was originally built for a 50 degree V-Twin engine,(J.A.P.?) and that it has been converted to 180 degree operation. The ‘cv’ suggests clockwise drive, with ‘acv’ for anti-clockwise drive.
Brian

[chstorm]

Hi Brian,

That is a very interesting observation. Whether the Scott factory had the conversion made (could be since the magneto is stamped TT on the top), or whether the original owner, John Henry Reynolds, made the conversion remains a mystery.
Reynolds made a number of changes to the bike (before 1933) for racing purposes -Webb forks, extra large petrol tank with central quick action filler, a large wrap round oil tank fitted behind magneto with LH quick action filler. Finned rear brake drum with 2 fins, short brake arm. Front brake drum drilled at back for extra cooling. RH footbrake, close ratio gearbox with LH footchange, possibly of KSS Velocette origin, mounted from the magneto platform. Amal carburettor Radiator with LH filler and larger than standard header tank. Left hand 2 into 1 exhaust system with Burgess silencer.

I find that I have sent information about the magneto to Chris earlier, together with photos. He obviously is looking for another type magneto, more correct for his bike.

Kind regards,

Carl

[BRIAN MARSHALL]

That must be the ex-Ian Parsons bike ?!

[Orgasmatron]

Brian and Carl, thank you both very much for your input.
Carl, when I showed Stuart Towner (who is attempting to source the magneto for me) the photographs that you very kindly sent me, his advise was the same as Brians (ie that it is a V-Twin magneto, possibly, as you say, adapted for racing).
So, as I am intending run my TT Rep without lights (although the records indicate that they were actually fitted by the factory), I wish to find a magneto that would have been fitted to a 1930 TT Rep. Brian’s comment that it should have the large taper with the male thread and nut helps (thank’s again Brian) and I now need confirmation of the model of BTH (I definitely want a BTH rather than a Lucas item). So, should it be M2 or MC2 ?
Chris.

[BRIAN MARSHALL]

I THINK that the M2 was a magneto made (originally), without provision for advance-and-retard mechanism, and usually employed on flat-twin stationary/portable engines such as those made by Douglas and Norman, driving things like water pumps and generators. A lot of these appeared, (unused), in ex-War Department Sales up to about 25 years ago, and they had been intended for use on portable aircraft-starting auxiliary engines. They had aircraft-type shielded pick-up holders, and can be converted for bike use by adding the advance-and-retard bits, and by changing the pick-up holders. Barry Bassett did one for me years ago. I also THINK that MC2 was the proper motorcycle version, with the A&R mechanism fitted. I don’t know what the MD2 mags were intended for. It should be noted that these different versions, whilst of similar appearance, had different numbers of turns in the windings, and for instance the aircraft-starting mags were intended to give a big fat spark at low revs, and they do not take very kindly to sustained high revs. Do not forget that a two-stroke mag has to run at engine speed, while a four-stroke mag runs at half engine speed, and thus has a MUCH easier life. Talk to an expert for confirmation of all this !
Brian

[BRIAN MARSHALL]

I’ve just Googled ‘Norman T300 Mk 1’ and found a couple of videos which both show what appears to be BTH M2 mags, without provision for advance and retard, so this tends to confirm my previous comments. Later versions show a bigger, impulse type magneto, (‘flicker mags’ in stationary engine enthusiast jargon).
Brian

[Martin Heckscher]

Hallo Brian & all,
As I have an original BTH M1 & M2 instruction book, I feel I had better put the record straight before it becomes accepted as magneto “fact” – these magnetos were most certainly supplied with an advance retard mechanism – it is there in print, in a photo and in 2 diagrams. I think I’m right in saying that the difference between a “K” & “M” magneto (not just BTH) was in the height of the armature above the base plate. I don’t know the differences between an M2 & MC2, but I am under the impression that an M2 was probably part of the standard spec of a Rep without lights – but it is well documented that as the factory lurched from one financial crisis to the next, they almost certainly fitted what the could get at any particular time, and were frequently forced to make changes to individual machines because preferred suppliers put them on “stop”.
Best wishes
Martin

[chstorm]

Hello Brian,

You are quite right, as usual. My bike is indeed the ex-Ian Parsons bike, which I bought from him in 2007. How time flies!

Kind regards
Carl

[Orgasmatron]

Very interesting discussion indeed. So, if both the BTH M2 and MC2 were manufactured in 1930 (is this the case, or is the M2 actually an earlier model?) the bike could have been fitted with either ; if this is the case, which would work better on the bike?

[Martin Heckscher]

Personally I wouldn’t worry about which type of mag it is. Just fit one which works properly. The key to happy vintage motorcycling is a good magneto, especially with a Scott, where the mag has a hard time because it runs at engine speed.
Martin

[BRIAN MARSHALL]

I am trying to get to the bottom of this subject, and have found a really excellent section in the ‘Radco’ book “The Vintage Motorcyclist’s Workshop” (highly recommended, and recently reprinted, so easily available again. They were fetching £200 a copy on eBay until about three months ago !). Pages 158 and 159 chart the differences between K and M type magnetos, and also compare them with the German standards. For instance a British A2 magneto should have similar dimensions to a German ZA2, and as I stated, anything with a V in it’s type number was indeed originally a V-twin magneto. On page 160 it also confirms,and I quote, “During the last war BTH turned out some very nice single and twin-cylinder stationary engine magnetos with fixed ignition. These crop up brand new from time to time. The lack of advance-and-retard facilities can be overcome by fitting a vintage BTH contact breaker housing, which will usually go straight on without further modification”.
What we are faced with 70 to 80 plus years later can easily be a mongrel, that has been modified any number of times in desperate attempts to keep a bike going during the long years before our vintage machines began to be appreciated, and specialist magneto repairers began to reappear. I am so glad that my previous comments have been affirmed by a real expert, the late Frank Farrington.
Brian

[Martin Heckscher]

You are absolutely right about the stationary engine magnetos Brian. The one currently on my Sprint had just such an origin, and my mag man grafted on the necessary advance/retard bits. That particular mag still bears an air ministry stamp.
Martin

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