A7 Motor with odd Suffix

[Lightningpower]

Hi, I have an A7 motor with a "D" in it.  Any ideas of what it stands for?

[dpaddock]

Well, since no one else has responded so far, I'll give it a shot: it's probably an engine made for the Daytona race event ca. 1954. I have no proof of this, although I've been looking. My reasoning is as follows:

BSA Gold Stars set up for Daytona were frame-numbered CB32D and their engines were BB34GSD, for the 1954 event only. This was done to satisfy AMA Class "C" rules which required that a minimum number of any motorcycle model raced under AMA auspices had to be offered to the general public for sale. This number was, I believe, fifty or a hundred. The purpose of this rule goes back to the Great Depression Thirties when local racers were uncompetitive because high-priced factory riders and exotic, 4-valve whiz bang bikes (Harleys and Indians) were being used to strictly promote sales; inasmuch as "all politics is local", spectators lost interest, unable to see their local riders contend on equal footing. AMA created Class "C" to eliminate this problem. In fact, Class "C" events were "claiming races" (for a while) wherein anyone with the minimum fee could buy the winning bike; as you can imagine, this helped to keep the factories honest.

Anyway, you might have the engine (or at least the cases) from one of these Daytona engines.

I'll sit back now and watch the fur fly.

David

[trevinoz]

Dave,
             I like your reasoning.
I have no idea so I will go with you.
One point, however, is the number itself - ***
Series started at *** so this is the second of it's run.
Trev.

edited, request from Lightningpower

[Lightningpower]

This is an interesting idea.  Dual port head in '53?  It is a semi-unit plunger motor so probably a 53 as aopposed to a '54.

If BSA did have to make 50 or 100 machines for homolgation purposes, would they all be stamped with a "D" as well?

[dpaddock]

Lightningpower: I expect all of the engines built to comply with the homologation requirements would be so stamped. The two-port head would have been proper for the Star Twin which was the basis for the 1954 Daytona engines.

Trevor: I expect BSA (who always started any series with "***", as you state) did so with this run,too.

Again, pure speculation on my part!

David

edited, request from Lightningpower

[Lightningpower]

According to Roy Bacon's BSA Twins and Triples book (page 128), AMA rules barred the BSA twins in Daytona 1954, because the frames were "not considered to be factory produced, but under pressure from BSA American distributors this ruling was reversed."  So, maybe they never made homologation machines?

[Lightningpower]

Now I've found the opposite message in another book, that says BSA claimed to have 100 machines made to comply with homologation rules. 

[trickytree]

Some info on the Daytona bikes HERE

[Lightningpower]

Still waiting for confirmation from BSAOC UK, but it is unlikely that they will have the number in the despatch records if it is a works racer, although it is possible.  I have been emailed from some of lads who know as much about Daytona A7 as anyone, and they are confident that my motor is, in fact, a Daytona.  How exciting is that?  It is unlikely to be "homologation" machine, but instead a genuine article racer.  Now... where's the rest of the bike?

[Lightningpower]

It's been a while since I've updated this thread.  I did get a reply from the BSAOC UK.  They tell me that my motor was from a "Special Racing Twin"  from 1953.  It was one of 13 built.  One went to Canada, two to Portugal and the rest the US.  I wish I knew what the frame was.  Could be rigid or plunger?   I would guess it would look like the 1953 Daytona machines, with plungers (the super-flash type frame), and alloy dual-carb heads.  That means that I have the correct head.  I would guess that the gearbox would have a DAY or DAYT ratios.  Doubt that will fall into my lap!