BSA Owners' Club Workshop Discussions

The BSA Workshop => Twins => Topic started by: chrisx1 on 28 Mar, 2023, 10:50

Title: Carb connecting studs
Post by: chrisx1 on 28 Mar, 2023, 10:50
can anyone please tell me the thread sizes for the carburettor studs. I need to re-tap the head and re-thread the studs both to the head and carb.
Title: Re: Carb connecting studs
Post by: Spaceman on 28 Mar, 2023, 11:14
Part 68-0018: 5/16" dia with BSF on one end and BSC the other. Length seems to differ among suppliers but ~1 3/8".
Title: Re: Carb connecting studs
Post by: chrisx1 on 28 Mar, 2023, 16:34
Does the BSC thread into the head?
Title: Re: Carb connecting studs
Post by: Spaceman on 28 Mar, 2023, 17:14
The coarse thread (BSF) should go into the soft aluminium of the cylinder head. However, I would get a 5/16" BSF bolt and double check that it appears to screw into cylinder head just to make sure a previous owner hasn't changed the thread!
Title: Re: Carb connecting studs
Post by: chrisx1 on 28 Mar, 2023, 17:34
sorry Spaceman is that a typo? bsf is fine bsc or bsw are coarse.
Title: Re: Carb connecting studs
Post by: chrisx1 on 28 Mar, 2023, 17:38
I've just had a thread checker on it and it seems to be 22tpi on the end that came out of the head which seems to equate to 5/16' BSF.
Title: Re: Carb connecting studs
Post by: Spaceman on 28 Mar, 2023, 17:56
The coarse is 22 tpi BSF and fine 26 tpi BSC
Title: Re: Carb connecting studs
Post by: chrisx1 on 28 Mar, 2023, 18:11
Ok, great thanks again for your help. Ive ordered a 5/16'BSF tap to clean up the head threads. and ordered new studs, as the original ones are buggered.