The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: chicago on 07.06. 2012 14:37
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hi there, im a little confused at the moment and was wondering if anybody on here can clear things up for me.
i bought what i thought was a 1953 bsa a7 star twin with a 1947 a7 longstroke engine. i sent for a dating certificate from the bsa owners club but on the certificate has come back saying its a 1953 650cc a10 golden flash frame with a 1947 a7 engine *conf* *conf* *conf*. the frame number on my bike states...
BA7.S.1086*(five numbers long *to replace last digit). i had a look on the bsa owners club frame and engine number listings
http://www.bsaownersclub.co.uk/Engine_Frame_Listing.html
and acording to that it says BA7S.101 is a star twin plunger.
and surley a bsa a10 golden flash would start with a frame number of BA10 no ?.
slight difference in the format of my frame number and the frame numbers on the bsa owners club website also.
my frame number format is......
BA7.S.1086*
and website frame number format is.....
BA7S.101
my frame number has 2 dot's stamped, 1 before the "s" and 1 after the "s"the website frame number only having 1 dot after the "s".
so is my bike a a7 star twin, a standard a7 or a a10 golden flash. cheers in advance fella's. all the best, chicago
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and surely a bsa a10 golden flash would start with a frame number of BA10 no ?.
No all A10s had frame numbers starting A7 apart from the Super Flash and Rocket Gold Stars
but such lists as I've looked at suggest a 500, suggest you check that the engine number matches the year number of the frame, you may already have done so I think
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and surley a bsa a10 golden flash would start with a frame number of BA10 no ?.
No all A10s had frame numbers staring A7 apart from the Super Flash and Rocket Gold Stars
but such lists as I've looked at suggest a 500, suggest you check that the engine number matches the year number of the frame, you may already have done so I think
cheers bsa bill, the engine in the bike is from a 1947 a7 (i think) XA7.137* so different numbers. cheers for the suggestion though, any idea about the dot before and after the "s" (ba7.s.1086* )all the best fella, chicago
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Hi Chicago, there seems to be a number of 53 plunger bikes fitted with long stroke engines sold recently. There was a 1953 A7 with a 48 engine sold on Ebay last month with a frame number of BA7.S.2107 so it also had a . before and after the S . In fact a lot of the parts on the bike were from a 1948 rigid including the QD front wheel and forks, rear mudguard, chain guard, front engine plates etc. Did anybody on the forum buy it ?
http://www.ebay.co.uk/itm/280867391371
Cheers, John
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Hi Chicago, there seems to be a number of 53 plunger bikes fitted with long stroke engines sold recently. There was a 1953 A7 with a 48 engine sold on Ebay last month with a frame number of BA7.S.2107 so it also had a . before and after the S . In fact a lot of the parts on the bike were from a 1948 rigid including the QD front wheel and forks, rear mudguard, chain guard, front engine plates etc. Did anybody on the forum buy it ?
http://www.ebay.co.uk/itm/280867391371
Cheers, John
hi there john, cheers for that fella, you must have a keen eye and an excellent memory to spot and remember the other bike on ebay having an extra dot. the bike on ebay was also described as an a7, same year as mine as well. the extra dot must have some form of meaning ??. all the best john and thanks for the info, chicago
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Once you understand the basics of BSA's numbering system its not too bad. I will try and explain it. First thing is BSA numbers do not match exactly, once again there are a few that do but most do not. So you are not likely to find a BSA with numbers that are the same on the frame and engine. When people refer to "matching numbers" on a BSA they mean the numbers both come from the same year and with a bit of luck left the factory together. The one exception here is the A7's from 48', I have seen a few of them that do have matching numbers.
I'm not going to include the Super Flash or the RGS or any "specials". The basic A7 and A10 numbering system covers 99.9% of them.
The first letter in both the frame and engine numbers denotes the year, however they sometimes used the same lettter for a few years, for example Z was used for 4 years, from 49' to 52'.
All A7's and A10's have A7 stamped in the frame regardless of wether they had a A7 or a A10 engine.
The dots dont mean anything, it was purely depending on who was on shift when the numbers were stamped, some used them and some didnt.
The S in the frame denotes sprung frame (plunger). It appears that when the sprung frame was introduced in 49' the rigid frames built from then on had a R stamped in but none of the dating information available records there being a R.
The engine numbers also use the first letter to denote year, for example Z. The second letter and number denote a A7 or A10. Special models like the Star Twin have an extra letter stamped and that is where it gets a bit difficult to explain as you have a S for Star Twin, SS for Shooting Star, RR for road rocket and so on. So an example would be a 49' A7 Star twin which would have a engine number ZA7S 101. but a standard A7 would have ZA7 101. The numbers increase as the bikes where built. The only way you can know if your bike has the engine in it that it left the factory with is to get the numbers checked against the factory records.
Chicago your engine number of XA7 is a 47' "Longstroke" A7. Your frame BA7 S 1086 is a 53' plunger frame and could have left the factory with either a A7 or an A10 engine. Just about everything with the plunger A7 and A10 models is interchangeable which explains why you see bikes for sale which are a mix of years.
Hopefully this has helped and not made it even more confusing.
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hi there brian, cheers for taking the time to give a in depth and very well explained answer.
thing is ive just been looking at a dating certificate from the vintage motorcycle club that came with the bike and the lady who issued the certificate (annice) has written in a foot note.......
"just to complicate things further *eek* it's a 1953 (1954 model) with a 1947 (1948 model) engine !"
and ive just been looking on this site....
http://www.britbike.com/bsapitstop/dating/1951-60.html
and if you scroll down to 1954 frame numbers it says.....
1954
Model Engine prefix Engine sequence Frame prefix Frame sequence CC
A7S STAR TWIN PLUNGER BA7S 2001 BA7S 8950 500
so maybe has 54 frame number ???. *conf* *conf* *conf* *conf*.
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Definitely a 53' frame Chicago, the numbers for 53' start at 101 so yours being 1086 is early in 53'.
The website you have quoted is correct, the frame numbers for 54' start at 8950 so yours being 1086 puts it back in 53'.
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cheers brian. frame number ba7.s.1086* five numbers long, i just put a star* in on the end (1086*) when i posted the tread incase tealeafs were reading the thread. sorry for that i didnt make it clear. all the best, chicargo.
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Ah, I see.
In that case if your number is 5 digits, 1086* then it is a 54' frame.
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hi brian,i'm hopless when trying to explain things, sorry fella *red*
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Its all good.
So the long and the short of it is even though you have a 47' engine in a 54' frame you have basically a plunger framed "longstroke" similar to the 49' or 50' models.
Its good that so many parts are interchangeable but as you have found out it can get a bit confusing.
The end result however is you have a bike to ride and thats the most important thing. It great to have "matching number" bikes but at the end of the day they are just numbers, they dont make the bike go any better.
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Its all good.
So the long and the short of it is even though you have a 47' engine in a 54' frame you have basically a plunger framed "longstroke" similar to the 49' or 50' models.
Its good that so many parts are interchangeable but as you have found out it can get a bit confusing.
The end result however is you have a bike to ride and thats the most important thing. It great to have "matching number" bikes but at the end of the day they are just numbers, they dont make the bike go any better.
hi again brian, so going off what annice writen as a footnote on the vintage motor cycle club dateing cert.....
("just to complicate things further it's a 1953 (1954 model) with a 1947 (1948 model) engine !")
and the frame has been stamped up with 1954 frame numbers i.e ba7.s.1086*....
and along with the frame numbers on the previously mentioned website....
Model Engine prefix Engine sequence Frame prefix Frame sequence CC
A7S STAR TWIN PLUNGER BA7S 2001 BA7S 8950 500
A7 PLUNGER BA7 2001 BA7S 8950 500
does that not mean that its either 1954 a7 plunger frame or a 1954 a7 star twin plunger frame that was very near to the end of the line of production and just before the shooting star was introduced?? and not a 1953 650cc a10 golden flash frame as the bsa dateing certificate says. ?????????. sorry but it really is confusing. all the best chicago
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Going by the info I have in 1954 only the A7 Star Twin and the A10 had a frame with the B prefix. The standard A7 had frames with a C prefix. By what the BSAOC sent you it looks like your frame left the factory with a A10 engine.
1954 seems to be a strange year as that was the year they introduced the swingarm frames and they list 9 different models.
A7 plunger
A7 swingarm
A7S Star Twin plunger
A7SS Shooting Star swingarm
A10 plunger
A10 swingarm
A10SF Super Flash plunger
A10SF Super Flash swingarm
A10R Road Rocket swingarm
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hi brian,
"The end result however is you have a bike to ride and thats the most important thing. It great to have "matching number" bikes but at the end of the day they are just numbers, they dont make the bike go any better."
i agree and no matter what it ends up being i will still love it to bits.
its just that to me (no expert at all) things just dont seem to add up to it being a 1953 a10 golden flash (nothing against a10's also beautifull bike's) according to the dateing certificate from the bsaoc the bike was despatched to "robert bevan and son, cardiff" i managed to contact the shop and it is still there and ran by the same family, i asked if he had any sales records from the time of the sale of my bike but unfortunatly he said that is the only year he had no record as they had a leak and it destroyed most of the records for that year, he said "the reg isnt a local one for cardiff though which was odd" when i had myself traced the area code for the reg on my bike (usy 180) it came back as being first registered in glasgow, scotland ???.
something else that does'nt quite add up is that on the bsaoc dateing certificate it says "1953 650cc a10 golden flash" but on the bsaoc website for the 1953 golden flash the frame numbers start at ba7s 101 surley they couldnt have made over 10 thousand a10 golden flash's in a year ??? as my frame number starts at ba7.s.10 thousand 8 hundred and odd ??? so surley cant be a 1953 as stated on the dateing cert ??? so if they can be wrong about that they may also be wrong about other things maybe.
if i am wrong then please forgive me as i am fairly new to the world of bsa
all the best fella, chicago
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Hi Chicago. Felt I had to chip in with my 2pence worth. Your bike obviously started life as an A10 (the highest percentage of all plunger bikes were A10) It is a 1954 YEAR MODEL which was manufactured in 1953. The factory started production of the next years model when they restarted after the summer break/shutdown which is why the number is over BA7.S. 8950. (I have a 1954 year model A7 Star-Twin, frame number BA7S 1162* that was despatched late 1953) The factory despatch records are the only way to tell which model the bike started life as, as the same frame number sequences were used for the standard A7, The A7 Star-Twin and the A10. The UK reg number is an age related re-issue (which often use Scottish registrations) The original reg number has either been lost or sold off. You would be a brave man to accuse Annice of being wrong as her Knowledge of the factory records is amazing! So to sum up, You have a 1954 model year A10, despateched in 1953 that is currently fitted with an earlier A7 engine, sadly not the Star-Twin you were hopeing for. Regards, Spanersc
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Hi Chicago, slightly off theme but I was wondering what front engine plates your bike has as the earlier long stroke A7 had a different shaped engine plates than the later short stroke A7 and A10 ? To add to the mix, the ones for 47/48 A7 did not have a hole for the dynamo in the drive side one as they used the shorter LUCAS E3HM dynamo (see pic). As a note if anybody has a 47/48 drive side plate spare then please let me know.
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Hi Chicago, sorry but you aren't the first person and I'm sure you won't be the last to be confused by the way BSA worked ,not for nothing were they nicknamed a " B it S tuck A nywhere " seems that included there marking system. In truth it must have something to do with the old way they used to plan out there production and marketing ,new models ,really upgrades were worked on/tested during the current production year ie 1953 but as they always showed off the next years models etc in november at the motor shows at earls court etc from about june they considered they were working on next years bikes. Also has the US was the main market and it was a very short peak marketing period they were always working to advance dates . I worked for 2 main dealers in Liverpool during the mid sixties and after march in a year if you reordered the bikes could come through in a different spec than the earlier ones ,who said continual development was new , shame it was only cosmetic and important things like new models ,triples etc took forever to appear . In fact one dealer wouldn't reorder for themselves after may to avoid having NOS bikes , an absolute shambles . best of luck BobH
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Hi Chicago. Felt I had to chip in with my 2pence worth. Your bike obviously started life as an A10 (the highest percentage of all plunger bikes were A10) It is a 1954 YEAR MODEL which was manufactured in 1953. The factory started production of the next years model when they restarted after the summer break/shutdown which is why the number is over BA7.S. 8950. (I have a 1954 year model A7 Star-Twin, frame number BA7S 1162* that was despatched late 1953) The factory despatch records are the only way to tell which model the bike started life as, as the same frame number sequences were used for the standard A7, The A7 Star-Twin and the A10. The UK reg number is an age related re-issue (which often use Scottish registrations) The original reg number has either been lost or sold off. You would be a brave man to accuse Annice of being wrong as her Knowledge of the factory records is amazing! So to sum up, You have a 1954 model year A10, despateched in 1953 that is currently fitted with an earlier A7 engine, sadly not the Star-Twin you were hopeing for. Regards, Spanersc
bsa certainly didnt make things easy to work out,
"You would be a brave man to accuse Annice of being wrong as her Knowledge of the factory records is amazing"
im sorry it wasnt quite clear on my post, i wasnt saying annice was wrong, i was saying maybe the bsaoc was wrong saying it was a 1953 .
"The UK reg number is an age related re-issue (which often use Scottish registrations) The original reg number has either been lost or sold off" *eek* nice one, please dont try and sugar coat it for me *smiley4*, if i said i wasnt a little dissapointed i would be lying. but at the end off the day i'm still happy with the bike and at least i didnt pay a fortune for it and i'm sure when i get to use it all this wont matter at all. cheers for the info fella, all the best, chicago
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Hi Chicago, slightly off theme but I was wondering what front engine plates your bike has as the earlier long stroke A7 had a different shaped engine plates than the later short stroke A7 and A10 ? To add to the mix, the ones for 47/48 A7 did not have a hole for the dynamo in the drive side one as they used the shorter LUCAS E3HM dynamo (see pic). As a note if anybody has a 47/48 drive side plate spare then please let me know.
hi there bikerjohndavies, not sure to be honest, but heres a photo of the one on my bike.......
http://i438.photobucket.com/albums/qq110/chicargo/SDC17550.jpg
i did have a quick look on ebay for you but didnt find anything, all the best fella, chicago
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Hi Chicago, sorry but you aren't the first person and I'm sure you won't be the last to be confused by the way BSA worked ,not for nothing were they nicknamed a " B it S tuck A nywhere " seems that included there marking system. In truth it must have something to do with the old way they used to plan out there production and marketing ,new models ,really upgrades were worked on/tested during the current production year ie 1953 but as they always showed off the next years models etc in november at the motor shows at earls court etc from about june they considered they were working on next years bikes. Also has the US was the main market and it was a very short peak marketing period they were always working to advance dates . I worked for 2 main dealers in Liverpool during the mid sixties and after march in a year if you reordered the bikes could come through in a different spec than the earlier ones ,who said continual development was new , shame it was only cosmetic and important things like new models ,triples etc took forever to appear . In fact one dealer wouldn't reorder for themselves after may to avoid having NOS bikes , an absolute shambles . best of luck BobH
hi there BobH, i thought bsa stood for Bloody Sore idiot *smile*. good bit of knowledge that, i just wonder what the situation in a couple of decade's or so will be regarding such info as most of the people around the bsa factory ect are sadly no longer around and i doubt if every bit of info has been documented. it makes you wonder. all the best fella and thanks for the info, chicago
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Hi Chicago, you have the later one as used on the 1949 onwards long stroke engines as it has a hole to allow the dynamo to poke out. I have scanned the autojumbles and the internet for the last year or so but no luck. What is really annoying is that I had a couple of them a while ago but decided I would never need them so moved them on. Lesson learnt, never sell anything.
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Hi Chicago, you have the later one as used on the 1949 onwards long stroke engines as it has a hole to allow the dynamo to poke out. I have scanned the autojumbles and the internet for the last year or so but no luck. What is really annoying is that I had a couple of them a while ago but decided I would never need them so moved them on. Lesson learnt, never sell anything.
i must tell you the number of time's ive done exactly the same thing and lived to regret it. the problem is now though that my garage looks like a hoarders garage with all manner of things packed to the rafters and hardly enough room for the bike.
i will keep on looking on ebay for you though as im on there quite a lot. all the best fella, chicago
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.....the problem is now though that my garage looks like a hoarders garage with all manner of things packed to the rafters and hardly enough room for the bike.....
If you have already reached that stage and you've not yet got your full bike licence I dread to think what your place will be like in 20 years time! Have you got room to build an aircraft hangar?
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.....the problem is now though that my garage looks like a hoarders garage with all manner of things packed to the rafters and hardly enough room for the bike.....
If you have already reached that stage and you've not yet got your full bike licence I dread to think what your place will be like in 20 years time! Have you got room to build an aircraft hangar?
hi there fido, thats if im still around in 20 years, i'll prob be found crushed to death under a pile of junk in my garage *smile*, all the best fella, chicago