New to owning bsa and advice needed.

[staffs]

Hi, I have had many classic bikes over the years but am new to owning BSAs. Me and a mate have just acquired a few BSAs with quite a lot of spares. I am sure there will be many questions to ask as we get into what we have actually purchased as I am sure we are going to need help identifying stuff and also finding out if we have bought a load of mongrels with the bikes. It was one of those purchases that had to be done there and then or walk away and regret it for the rest of our lives so had very little time to study what was what. I am hoping you guys and gals will help steer us along. So here are a few to start please. We have some Gold star barrels in various condition, some are the small fin and some the large fin type. When did they change or were the big square fin type an optional option. Did the 350 and 500 share the same casting but had a different liner fitted.
Are crankcases matched and numbered in pairs. I have two good timing side and one good drive side crank cases for an A10 and I cant see any stampings to pair them up. Does it even matter?
Where can I get N1? M01L magneto spares or an electronic ignition system.
Your advice will be much appreiated
Thanks Staffs

[AWJDThumper]

Hi and welcome to the forum.

I'm not an expert on pre-unit singles and so will leave the other experts on the forum to answer those questions. In terms of the crankcases, the engine number identifying them is only normally stamped on one of them - I'm not sure there is any way of tell whether crankcases are actually a matched pair. In general, all crankcases should be matched to ensure the bearings for camshafts, crankshafts, etc are precisely aligned in the two halves. That said, it is possible with a bit of luck to use mis-matched crankcases but there's no guarantee you won't end up with tight shafts in bearings. It's all about tolerances.

[JulianS]

If you carefully examine the cases around the outside edge near the centre joint you may find a number, the ones I have seen are 3 digit, stamped on each case half. If they are the same the cases are a matched pair.

Not to be confused with the engine number.

[Bess]

Hi,
     I have attached an image example for Julian's description....

Best wishes...

[JulianS]

Big fin Gold Star barrels started with the CB series. Small before that.

Not all light alloy barrels are Gold Star, small fin were used on the B32A and B34A non Gold Star competition models.

There are lots of Gold Star reference books available and most are well worth reading. Parts books would also provide some answers.

[staffs]

Thanks you for info on both subjects. I now realise I have muddled the singles and twins sub divisions. It wont happen again......unless its midnight and i have been to the pub
Staffs