The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Voldsgaard on 08.10. 2020 17:11

Title: Engine and frame numbers
Post by: Voldsgaard on 08.10. 2020 17:11
Hello *smiley4*

I bought a A10 GF this summer, but I'm getting confused with the frame and engine numbers, and I am not sure that I have understand it correctly.

Engine: CA108172.
Frame: GA7A2639.

From what I have read, is that my engine should be around 1956-57.
And my frame would from 1962-63.

Am I correctly?

The first registration of the bike is from 1960.
Is it possible that the previous owner have chanced the frame and engine, because the first registration is from 1960?

I hope you guys can help me  *smiley4*

Thanks in advance.

Niels
Title: Re: Engine and frame numbers
Post by: JulianS on 08.10. 2020 17:25
Are you sure of that frame number?

GA7A prefix was used on the A10 Spitfire Scrambler between September 1959 and September 1962. The highest number was in the 7 hundreds.
Title: Re: Engine and frame numbers
Post by: Swarfcut on 09.10. 2020 08:57
 If the numbers are correct the engine is certainly earlier than the frame. A later frame has an sheet metal strengthening wraparound running almost the full height of the steering head. On earlier frames (contemporary with the engine number) this only goes a third of the way up.

 Swarfy.
Title: Re: Engine and frame numbers
Post by: JulianS on 09.10. 2020 09:27
The wide steering head brace was introduced from around August 1960 for the 1961 season models.
Title: Re: Engine and frame numbers
Post by: Voldsgaard on 09.10. 2020 11:31
I will take some photos of the engine and frame number later today. And a few of the steering head.

I think it will help you guys.

I really appreciate the help.


Niels.
Title: Re: Engine and frame numbers
Post by: Voldsgaard on 09.10. 2020 15:58
I have taking the photos of the frame number and steering head, and a photo of the engine number.

On the frame number, I think it is a "G" but if it is a "C" it is my reading-mistake  *smiley4*

I hope it will help.


Niels.
Title: Re: Engine and frame numbers
Post by: Klaus on 09.10. 2020 16:37
Hi Niels,

It is an A10 Frame from 1960
The Engine ist one of the last in 1958
Engine Number CA10 R 8193 is the first in 1959

cheers Klaus
Title: Re: Engine and frame numbers
Post by: Klaus on 09.10. 2020 16:45
Ups, Framenumbers with GA7A are for Spitfire but they have only 3 Numbers.
Hm There must be something wrong, as shown in an other reply.
Title: Re: Engine and frame numbers
Post by: RDfella on 09.10. 2020 17:24
Have to say with the shape, form and spacing of the numbers (especially frame) it doesn't look like they've been messed with so must be original.
Title: Re: Engine and frame numbers
Post by: JulianS on 09.10. 2020 17:51
The engine is early 1956 season.

Title: Re: Engine and frame numbers
Post by: RichardL on 09.10. 2020 18:21
3.242 "CA10" engines after my '55.

Richard L.
Title: Re: Engine and frame numbers
Post by: KiwiGF on 09.10. 2020 21:16
The uk bsa club site has comprehensive info on frame numbers and shows GA7A numbers up to 1963.

I’m no expert but the frame number looks correct to me, only very slight doubt would be the number 2, which sometimes have a sharper corner on the bottom than 90deg (if that makes sense).



Title: Re: Engine and frame numbers
Post by: JulianS on 09.10. 2020 22:52
Look at the slight curve on the legs of the A and compare with the A on your own frames and see what you think.
Title: Re: Engine and frame numbers
Post by: Klaus on 10.10. 2020 02:06
I ask me why the forth, Number 9 is not in line with the others?

Klaus
Title: Re: Engine and frame numbers
Post by: Voldsgaard on 11.10. 2020 08:04
Good question, it's very hard to say what the previous owner did to the frame number, because you are right, number 9 is not in line with the others.

But I really learned a lot about my frame and engine, I really appreciate the help.

Thank you very much.


Niels.
Title: Re: Engine and frame numbers
Post by: RDfella on 11.10. 2020 12:35
If we are suggesting the last number has been added, then they've all been 'added' because the nine is exactly the same as the six, meaning the same set of punches was used for all. The spacing is not perfect either, but we must remember these would have been stamped by hand, not machine. Whatever, the GA7A is the important bit and the A cannot have been added in there. I'm perfectly happy to say that all those numbers are original.
Title: Re: Engine and frame numbers
Post by: JulianS on 11.10. 2020 13:11
The problem being that there were no 4 digit GA7A frame numbers.
Title: Re: Engine and frame numbers
Post by: KiwiGF on 11.10. 2020 21:07
Maybe we should have a ‘sticky” thread on how to spot incorrect frame numbers, and how to date a frame and engine as it does come up a fair bit.

It seems there are many reasons why a number was not actually stamped by BSA, some legit (new frame or case fitted) others obviously not so legit  *eek*

I know some like to keep the numbers “secret” but engine numbers are generally obvious for all to see, and as far as I can tell frames have the same stamping “font” .......frame numbers are less visible.....but here is a selection of engine numbers from this era for comparison (and two from a bit earlier).

A “feature” not so easily replicated is that in some years the BSA letters and numbers seem to be different heights!

Edit: I’ve no reason to think any of these numbers are not legit, but you never know eh.

Title: Re: Engine and frame numbers
Post by: RDfella on 11.10. 2020 21:25
Reason I made my earlier comment was because clearly the frame number we're discussing is of regular font. So either the whole number is genuine, or the whole number is fake. Clearly the next step is to compare with frame numbers either side, preferably in the same year, to see if it's a BSA font. I have several number / letter punches and none have the flourish the frame number pictured has.
Title: Re: Engine and frame numbers
Post by: Joolstacho on 11.10. 2020 23:45
I seem to remember that replacement crankcases were not stamped by the factory, the retailer was supposed to do it, (presumably to match the original number). Sometimes it might not be done, or might be done incorrectly.
My SR was used as a grass tracker and ran something around 14:1 comp ratio, the seller told me it had replacement crankcases (not surprising!) - it has no numbers.
Title: Re: Engine and frame numbers
Post by: KiwiGF on 12.10. 2020 02:26
Here are ‘two types if 2” I referred too earlier, I guess only one is “correct”!

Title: Re: Engine and frame numbers
Post by: bikerbob on 12.10. 2020 10:41
As Julian says there were no 4 didgit numbers for the GA7A frames also he has a valid point about the shape of the letter A stamping, the only way to verify this is to go through the dating certifcate proceedure with the BSA Owners Club. There are a number of dodgy frames about, I remember a number of years ago I bought a BSA C12 in bits to restore and from the same person I bought a donor bike that was complete except for the seat, now the donor bike had no paperwork because when I checked the frame number someone many years ago had ground off the original frame number and had strangely restamped it with a BSA C15 number. Looking at that number it looked like a perfectly good stamped number except fot it being a C15 number, it was only when you scraped the paint off that you could see the grinding marks.
Title: Re: Engine and frame numbers
Post by: Voldsgaard on 16.10. 2020 12:21
I do really appreciate your help guys.

My next step is to do the dating certificate procedure from the BSA owners club.

Thank you very much.


Niels.