The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Lightningpower on 29.06. 2010 00:20

Title: A7 Motor with odd Suffix
Post by: Lightningpower on 29.06. 2010 00:20
Hi, I have an A7 motor with a "D" in it.  Any ideas of what it stands for?
Title: Re: A7 Motor with odd Suffix
Post by: dpaddock on 29.06. 2010 19:52
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
Title: Re: A7 Motor with odd Suffix
Post by: trevinoz on 29.06. 2010 22:47
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
Title: Re: A7 Motor with odd Suffix
Post by: Lightningpower on 30.06. 2010 01:11
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?
Title: Re: A7 Motor with odd Suffix
Post by: dpaddock on 30.06. 2010 02:08
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
Title: Re: A7 Motor with odd Suffix
Post by: Lightningpower on 30.06. 2010 06:01
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?
Title: Re: A7 Motor with odd Suffix
Post by: Lightningpower on 02.07. 2010 06:59
Now I've found the opposite message in another book, that says BSA claimed to have 100 machines made to comply with homologation rules. 
Title: Re: A7 Motor with odd Suffix
Post by: trickytree on 02.07. 2010 23:06
Some info on the Daytona bikes HERE (http://www.beezanet.com/daytona/default.htm)
Title: Re: A7 Motor with odd Suffix
Post by: Lightningpower on 29.07. 2010 17:17
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?
Title: Re: A7 Motor with odd Suffix
Post by: Lightningpower on 14.10. 2011 06:48
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!
Title: Re: A7 Motor with odd Suffix
Post by: Lightningpower on 07.11. 2016 22:58
I see I've neglected this thread. I now have a picture of my bike (engine and pile of parts I've collected) on the beach at Daytona in '53 as well as a copy of the original Dyno test at BSA. For your information, the bike was a plunger framed machine with a single carb head. The head is alloy with a long inlet tract. Thanks for your help when I started figuring this out.
Title: Re: A7 Motor with odd Suffix
Post by: Greybeard on 07.11. 2016 23:04
Hi. I'd like to see that photo.
Title: Re: A7 Motor with odd Suffix
Post by: BSA_54A10 on 08.11. 2016 09:22
BSA had a habit of returning race shop specials to civilian spec and selling them once the race shop had finished with them.
So your motor could be one of these.
Title: Re: A7 Motor with odd Suffix
Post by: Lightningpower on 08.11. 2016 19:40
David - This machine was never repatriated. It went to western Canada and was a regular on local west coast tracks for a few years.

Greybeard- the photo of the bike on the beach is excellent. I acquired my copy from the family's archives, but have been asked not to share it with anyone. I'm not sure why it matters, the racer and his wife in their shorts and her bikini wasn't exactly 'racy.' I do, however, respect their wishes. The bike looks a great deal like a Super Flash.
Title: Re: A7 Motor with odd Suffix
Post by: BritTwit on 19.04. 2017 04:46
David - This machine was never repatriated. It went to western Canada and was a regular on local west coast tracks for a few years.

The 13th place finisher for the 1953 Daytona 200 mile expert race was Trev Deeley in B.C.  Could be a connection?
Title: Re: A7 Motor with odd Suffix
Post by: Black Sheep on 20.04. 2017 22:26
I can confirm that BSA returned race bike spec stuff to the service dept. Some years ago I picked up a standard bore service exchange set of thick flange small fin barrels and pistons, normally only seen on Daytona machines.
Title: Re: A7 Motor with odd Suffix
Post by: Joolstacho on 21.04. 2017 00:19
My late type pre-unit crankcases have no number at all. I was told by the feller who sold me the engine that when BSA supplied replacement crankcases BSA left them unstamped because they wouldn't know whether it would be used for an A10 or A7. Can anyone from back in the day confirm?
(Apparently it had been in a grass-track outfit which had previously had a blow-up).
Title: Re: A7 Motor with odd Suffix
Post by: JulianS on 21.04. 2017 09:06
See below BSA parts bulletin from 1954, last paragraph - yes they came without numbers stamped.

Sorry its a poor copy.
Title: Re: A7 Motor with odd Suffix
Post by: Joolstacho on 21.04. 2017 09:41
Well, mine must have escaped this bulletin (who'd be surprised? -It was probably friday arvo, - race to get down to the pub for a pint or six!)
(Note " should" not 'must')  ;)

Oh, and I bet more than a few disappeared out the factory gates in lunch bags too.
Title: Re: A7 Motor with odd Suffix
Post by: trevinoz on 22.04. 2017 00:14
This will give the purists something to think about.
There has been much discussion whether fonts on characters are correct from the factory or fraudulent.
Title: Re: A7 Motor with odd Suffix
Post by: Klaus on 04.05. 2017 22:40
I have found an enginecase stamped DR 150069 CAL  this is not an Ariel Number.
Does anybody know more about this Number.
May be Daytona, its only a suggest.

cheers Klaus