1954 A7 Gasket Set

[lutim]

Hey Guys,
I am restoring an 1954 A7 that I bought in boxes, not sure if it is also called the Star Twin. Kind of confused with buying gasket sets as there are ones with part no. BSA 315 for 1951-54 A7 Star Twin but am unable to find one for A7. As per my understanding, A7 was later in the early 50's named as Start Twin, but I have my doubts 

Please help.

[Topdad]

Hi Lutim, welcome to the forum ,I think you're our second member from the sub continent. The progress of the A7/A10 range started with a  long stroke engined bike from 1947? to 1950??  when they developed the A10 and changed the engine of the 500 to a short stroke. If yours is a '54 you'd expect it to be the latter but with BSA never take things at face value check . If you've got a Stat twin that would I think be quite rare even if it's a bog standard A7 IT'LL STILL BE A GREAT BIKE !!  there are many guys on here who know the range far better than I do so all you've got to do is ask. In the meantime why not post a little info about yourself ,how you got into BSA's( and other bikes )and add so pictures , enjoy your bike  ,best of luck, BobH

[lutim]

Thanks for the warm welcome    Cheers !

I have been into BSA's for a while now and have newly acquired 2 projects in boxes A7 and B33. I started with a B31 and enjoyed it for years before I had to sadly let go of her, but here I am again with 2 of the lot 

I would like to think that it is a Star Twin but still need to confirm before I raise a toast. You are right, its a good bike and I am just waiting to finish it, plan to do a cross country ride. Will post pictures of the build in progress.

Cheers !

[bikerbob]

Hi there.  If your bike is a 1954 Star Twin then the engine number should begin  BA7S- **** If it is 1953 it should begin BA7S-**** 1952 AA7S-**** 1951 AA7S-****  1950 ZA7S-****  1949 ZA7S-****  The important thing about the engine number regardless of the year is it should have after the A7 the letter S this denotes that it is a Star Twin engine.

[duTch]

 Hiya there Lutim, ...what the Bobs said, but I have the notion that the first A7 'Vertical Twin' was '46, which had a speedo-in-tank, and the 'Star Twin' was the 'sport' model from '47-> I could be dreaming, but also think these had engine prefixes with "X', and 'Y'...
 According to the info I have (Parts books), if it's a Longstroke stroke engine, or shortstroke A7 Plunger '49-'54-'57 will be a Star Twin, but if a swing Arm, will be a 'Shooting Star'....??

 Re; gaskets, I think all A7/10 are the same, except maybe the Head-gasket.... I make my own any way, partly 'cos I'm a cheapskate, and partly because some guys have issues with manufactured ones being not wide enough to cope with the mismatched mating surfaces that seems to be so common (rocker boxes, and on mine between the oil pump cavity, and dynamo-hum chain case )

   cheers for now

[bikerbob]

Hi there. I am quoting from Roy Bacon's book on the BSA twins. The A7 did start in 1947 and the engine numbers started with XA7 then YA7 in 1948 and ZA7 in 1949. The Star Twin first came out in 1949 and continued until 1954 with the numbers I listed previously I think the 1947 and 1948 models were rigid back ends and the plunger models started in 1949 alongside the last of the rigid back end ones and the first of the Star Twins.

[duTch]

 I meant to say the Head gasket stud patterns will be the same, just there may be smaller holes for the bores...?? You can make those too if you need to..

[lutim]

Thank You Guys for all your responses. I was doing my own research and did stumble upon the holy grail of BSA vin numbers by the years of manufacture and their engine number prefixes, have attached it for the benefit of all. Bikerbob was right when he said that the Star Twin would have a prefix with an 'S'. Sadly this means that mine is not a Star Twin but just an A7 but still this is the later one with better compression ratios so no regrets.

I will take on the advice given by duTch and will make my own gaskets which I have been doing on the other restorations i have done in the past, Just that this time got a little lazy and wanted to take a 'ready made' approach. The head gasket is fine so I need not worry about that one 

 

[bikerbob]

I make most of my own gaskets mainly the ones that you have to remove quite regular such as timing case and primary case, but I make mine out of sheet cork that way you can reuse a number of times. I use proper cork gasket material that has nitrile rubber mixed into it is 2mm thick it is time consuming to make them I made mine over the winter months but worthwhile. When I fix them to the bike I put a smear of gasket cement on one side usually the outer case and a smear of grease on the other side that way they come away cleanly and can be reused. Paper gaskets are normally a once only use if you use gasket cement.

[muskrat]

Every few years I buy a set and use them as templates bto make my own from either 0.4 or 0.8mm gasket paper. With a thin smear of blue silastic I can get at least two uses out of them.
Cheers