The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: RoadRunner on 12.02. 2011 21:53

Title: Matching numbers?
Post by: RoadRunner on 12.02. 2011 21:53
Here's one of those niave questions  *conf* and I have searched the forum (quickly).
I understand the the frame numbers and engines match with the year: for example a '56 Golden Flash A10, the frame number would be: CA10-8001 (onwards) with the engine number being: EA7-101 (onwards).

What I need to know fairly quickly is; did BSA make the numerical digits after the prefix's of CA10 and EA7 the same, for example, a '56 GF A10, frame CA10-9012 & engine EA7-9012?

Apologies for asking such a basic question but I'm going to view a bike and not quite convinced that it's original. *eek*

A humble thanks.

Title: Re: Matching numbers?
Post by: trickytree on 12.02. 2011 23:48
Please dont take this as gospel but i thought that matching numbers were brought in for the later unit twins. The answer is on BritBike forum somewhere (but there search function is next to useless so good luck finding it)
Title: Re: Matching numbers?
Post by: muskrat on 13.02. 2011 02:18
Short answer is NO. If you find one it's been re-stamped or a real fluke.
 I knew a fellow who sand blasted his Tri frame and found more than one #, lots more. *eek*
Title: Re: Matching numbers?
Post by: BSA_54A10 on 13.02. 2011 05:42
Engine and frame numbers were stamped as the units were made, regardless of what model the bike was, so if three consecutive engines on the line were an A7 then a a10 & then a A10R then their engine numbers would be ???1 , ???2 & ???3.
Same thing happened on the singles line so if the first twin for the year was 0101 and the last was 2101 that would mean that the combined output of all variations of the 650 & 500 twins was 2000 for that year, not that BSA made 2000 A10's as may "experts" claim.

Engine & frame numbers became identical when laws in various places demanded that they must be.

The exception to this is special contract orders so if the NSW Police ordered 200 alternator A 10's with 1/2 longer swing arms & higher compression pistons then these 200 bikes would have matching engine & frame numbers, oft something like GA10-AP101 to GA10-AP301 or GA10-101AHP to GA10-301AHP.
So it is possible to have matching engine & frames but the general rule is no.
Title: Re: Matching numbers?
Post by: Beezageezauk on 13.02. 2011 12:27
Hi RoadRunner,

For a 1956/57 swinging arm A10GF the frame number should be EA7-101 upover and the engine number should be CA10-8001 upover.  Frame numbers starting with a *A10 prefix were generally only found on the plunger Super Flash and Rocket Goldstar models but, as previously mentioned, there can always be an exception to the rule.

BSA introduced a new coding system for all models from 1969.   After this date all BSA's had actual matching engine and frame numbers and the new coding gave the year and even the month that the bike was made.


Title: Re: Matching numbers?
Post by: RoadRunner on 13.02. 2011 17:20
Hi Guys,
Thanks for the speedy responses as usual, it really helped to know what was what before travelling the 340 miles to view an 'original' '56 GF early this morning!

Turned out to be not so original but what is there is good if a little rusty *conf*. its also a '58 not '56.
Just got to decide what offer to lob in as there are 2 other offers already in [does need a complete restoration though!) ummm, a beer tonight and some hard thinking??

Question: Where abouts is the frame number located on the frame - couldn't find it on the down tubes and couldn't see anything on the head stock; but it is very rusty and propped up against a wall in dark room! And couldn't remove the tank or move the bike.

Thanks again for the prompt & excellent info.


Title: Re: Matching numbers?
Post by: brackenfel on 13.02. 2011 17:27
Hi Roadrunner,
Should be on the headstock above the bracing plates, running downwards, on the RHS side I think (from memory).. Often very faint, especially if the frame has been powder coated..

Title: Re: Matching numbers?
Post by: trevinoz on 13.02. 2011 20:20
                  Your statement that the engines were numbered consecutively regardless of model is incorrect, I think.
Norton did this but I am sure that BSA didn't.
Maybe this happened for the unit models but not for pre-unit.
Title: Re: Matching numbers?
Post by: Beezageezauk on 13.02. 2011 20:43
Ok RR,

If it's a 1958 model the frame number should be between FA7.101 and FA7.8521.  The engine number should be between DA10.651 and DA10.4615.

Title: Re: Matching numbers?
Post by: RoadRunner on 13.02. 2011 21:35
Thanks guys,

If my offer is accepted I'll search the headstock for the frame ID (cheers Brackenfel).

As for the year - saw the log book which stated it was a 1958 with the frame Nos: EA7 1xxxx and engine Nos: CA10 1xxx? From the BSA ID list these are correct for a '56?

As you say Beezageezauk the numbers for a '58 are different to the above - whoops? I guess DVLA could have made an error when transferring from old log book to new V5? Is it possible to change the V5 I wonder?

I don't know much about the swinging arm models (yet) but the tank has the large round badges if that helps ID the correct year? If I'm lucky enough to get this rust bucket no doubt I'll be posting stacks of more novice questions having spent my time getting to know my plunger (which I must finish first!).

Keep you posted!


Title: Re: Matching numbers?
Post by: brackenfel on 14.02. 2011 07:17
Hi Roadrunner,
Unless your memory is a lot better than mine I'd print off the relevant page of this and take it with you :-

Tanks are easily interchanged on the swing-arm models but round badges are correct for 1958-1959.. 1960 onwards had the longer pear shaped ones. I think that 1956 bikes may have had the "winged" type as I have a friend with the alloy hub model with these, can't remember what year it was - I'm sure someone will correct me..

Good luck!


Title: Re: Matching numbers?
Post by: Beezageezauk on 14.02. 2011 10:14
Hi again RoadRunner,

The easiest way to determine the year of the bike would be with the wheels...but it all depends on how genuine the machine is.  1956 and '57 Golden Flashes used the same engine and frame numbering prefix and these were fitted with the "Ariel" type alloy full width hubs.

For 1958 models BSA fitted the cast iron full width hubs so this is the first thing to look for when determining the year.  To change the front wheel would mean changing the front fork legs to suit so it's not a simple job.  Fuel tanks often got damaged (or leaked) and were easily replaced so I wouldn't go by that.

The bike in question could be a '56 or '57 model even though, as you say, it shows 1958 in the log book.  The log books show the date of registration, not the date of manufacture, and the bike could have been stood in a showroom for several months before it was sold.  Hence, a '56/57 model registered in 1958.

I have a B31 that left the BSA factory in February '58 and wasn't registered until March '59.  For years I thought it was a '59 model!!

Hope this helps.

Title: Re: Matching numbers?
Post by: RoadRunner on 14.02. 2011 10:49
Hi Guys and thanks for all the excellent info again,

The wheel hubs are full width, rear brake plate on RHS; see low res pics below - don't know if anyone will be able to view them ok or not?
All the info is brill and gives me a solid basis for IDing this bike or/and future ones' if my offers not accepted. Not sure I'm doing the 'right' thing by attempting to buy it but...... not doubt will regret at some point in the future if I do! Domestic duties may double I guess?
Keep you posted and fingers crossed.

Title: Re: Matching numbers?
Post by: brackenfel on 14.02. 2011 14:00
Hi Roadrunner,
Pic one, rather difficult to see but looks like a full-width Ariel alloy type, fitted from 1956 to 1957. Pic two - rear one is full width later type, fitted from 1958 on..!! I'd check this bike carefully, it may be built up from parts!! On the other hand if the frame & engine numbers are from the same year then maybe someone just fitted a different hub at some stage.. All good for negotiating the price though...

Good luck,
Title: Re: Matching numbers?
Post by: Beezageezauk on 14.02. 2011 15:30

I'm agreeing with Adrian.  Earlier front wheel and later rear.  And from what you are saying, early engine and frame number but later fuel tank!!

Next question.  Can you remember if the headlamp is covered by some sort of shroud or nacelle that houses the lighting switch and speedo?  If it is can you describe it?  Maybe you have a picture of the speedo area? That could give us another clue.

But ultimately it would all depend as to whether the actual frame number matches up with that on the log book.

Title: Re: Matching numbers?
Post by: RoadRunner on 14.02. 2011 16:00
Hi Guys,
Don't like the sound of where this is heading!
But best to know in advance I guess - saves adding to my collection of parts that don't fit/match or even wrong bike ;)

The headlight area does have a nacelle and did have a old style police fairing fitting (just been removed), there's no full length fork shrouds visible, it has gaiters which may be over the shrouds??

The speedo is a Smiths but not one I've seen before - pardon the description - it looks like a simplified version, the face isn't like my regular A7 type?
The m/guards aren't there either - just some old alloy bits made up, I presume it should have full valanced guards with the usual stays or did some A10's get chromed sporty guards??

Anyway not parting with cash until I know more.. thanks again for the info, by the end of this I'll owe a few beers.
Ummmmm...... slighty less enthusiastic now...


Title: Re: Matching numbers?
Post by: brackenfel on 14.02. 2011 17:12
Hmmm, beer.... now you're talking.....
This bike sounds like a challenge if you want it to look anything like BSA intended... !!
Here's a couple of photos, I'm sure others will have better ones but in the meantime.. First is the 1954-57 "Diving Helmet" type (my B33), second is the A10 nacelle fitted from 1958 onwards.. Some bikes had a much more attractive separate headlamp (Super Rocket etc) but these two types are the more common:-

Hope this helps.. Keep it up, we're dying to see more of this project!!

Title: Re: Matching numbers?
Post by: Beezageezauk on 14.02. 2011 21:24

This is sounding more like a project that's going to run away with some cash.  As well as a complete renovation it will need a host of parts over and above a normal restoration.  Unless it's reasonably cheap I would think good and hard about it and even then, only if the paperwork matches up.

Sorry if this seems like doom and gloom but I'm just trying to be realistic!!

Title: Re: Matching numbers?
Post by: RoadRunner on 14.02. 2011 21:37
Hi Beezageezauk,

Thanks (and I do mean that in a +ve way) - and I'm inclined to agree, been there before and still yet to finish my first project which has cost an absolute stack of beer beans! But it's looking good  *smiley4*.

The more I learn about this 'original' '56/8 GF the less I'm inclined to part with any money - would be good for spares at the right price but doubt it go for a realistic price. So I really appreicate everyone's honest opinions. I'll see what response I get to my offer!

RoadRunner  *conf*
Title: Re: Matching numbers?
Post by: brackenfel on 14.02. 2011 21:54
Agree with beezageeza UK on this I'm afraid..

A 1956 bike should look like this 1957 one, recently on ebay (Ebay no: 180625613193 )

Title: Re: Matching numbers?
Post by: Howard on 15.02. 2011 08:18
Hi RR,For my 51 A7 has  I got a dating certificate from the BSAOC and it states that the engine is the original item for that frame.It also says that the original colour was black and it came with sidecar gearing and also the exact date of first registation. So it may be worth paying the £10 if your are not a member (£5 For members) and get a dating cert.
Title: Re: Matching numbers?
Post by: RoadRunner on 15.02. 2011 08:45
Cheers Howard,
Sounds like a good plan so if I decide or get the chance to buy at the right price I'll do that.
Just a waiting game now I guess  *eek*

RoadRunner ???