Author Topic: bsa a7 star twin or a10 golden flash ?????  (Read 5509 times)

Offline chicago

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bsa a7 star twin or a10 golden flash ?????
« on: 07.06. 2012 14:37 »
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
Location: north west madchester.
Preferred location: somewhere warm and dry.
Bike: 1953 plunger Longstroke engine.

Online bsa-bill

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #1 on: 07.06. 2012 15:05 »
Quote
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

All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline chicago

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #2 on: 07.06. 2012 15:14 »
Quote
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
Location: north west madchester.
Preferred location: somewhere warm and dry.
Bike: 1953 plunger Longstroke engine.

Online bikerjohndavies

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #3 on: 07.06. 2012 18:24 »
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
1937 Panther M100 Rigid, 1946 Ariel Square 4, 1952 Norton Model 7, 1953 BSA A10SF (WIP), 1958 BSA C15, 1961 Triumph T120R

Offline chicago

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #4 on: 07.06. 2012 23:28 »
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
Location: north west madchester.
Preferred location: somewhere warm and dry.
Bike: 1953 plunger Longstroke engine.

Online Brian

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #5 on: 08.06. 2012 00:53 »
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.

Offline chicago

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #6 on: 08.06. 2012 01:26 »
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*.
 
Location: north west madchester.
Preferred location: somewhere warm and dry.
Bike: 1953 plunger Longstroke engine.

Online Brian

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #7 on: 08.06. 2012 01:41 »
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'.

Offline chicago

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #8 on: 08.06. 2012 01:50 »
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.
Location: north west madchester.
Preferred location: somewhere warm and dry.
Bike: 1953 plunger Longstroke engine.

Online Brian

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #9 on: 08.06. 2012 01:56 »
Ah, I see.

In that case if your number is 5 digits, 1086* then it is a 54' frame.


Offline chicago

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #10 on: 08.06. 2012 02:00 »
hi brian,i'm hopless when trying to explain things, sorry fella *red*
Location: north west madchester.
Preferred location: somewhere warm and dry.
Bike: 1953 plunger Longstroke engine.

Online Brian

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #11 on: 08.06. 2012 02:10 »
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.

Offline chicago

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #12 on: 08.06. 2012 03:56 »
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
Location: north west madchester.
Preferred location: somewhere warm and dry.
Bike: 1953 plunger Longstroke engine.

Online Brian

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #13 on: 08.06. 2012 04:16 »
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

Offline chicago

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Re: bsa a7 star twin or a10 golden flash ?????
« Reply #14 on: 11.06. 2012 00:42 »
hi brian,
Quote
"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
Location: north west madchester.
Preferred location: somewhere warm and dry.
Bike: 1953 plunger Longstroke engine.