so your brake light switch has failed and it's the banjo switch on the master cylinder. your unsure what fits what out there, well I know for sure on the baggy it M10 X 1MM, however, .heres a list of what other bikes mostly use.
Thread Guide
Please note this guide is to help you choose the correct thread but you must check the bolt against the one you are taking out to ensure you have the correct fit
and to avoid damaging your parts, it is given in good faith but there are exceptions
Aprilia, Bimota, BMW, Cagiva, Ducati, Moto Guzzi, Brembo* ATE use M10x1
Harley Davidson
Up to 2004 Single disc models use 3/8x24 on the Caliper and 7/16x24 at the master cylinder,
Twin disc models use 3/8x24 throughout, Post 2004 they use a combination of M10x1 & M12x1.5
Honda
Most use M10x1.25 with the exception of the CB500 and some parts of the early linked braking systems found on Goldwings and Deauville's
Kawasaki
Post 1978 All use M10x1.25 but earlier models can have M10x1
Suzuki
Pre 1994 use m10x1 through out, between 1994-2004 they use a combination of both M10x1 & M10x1.25, post 2004 they are supposed to be all M10x1.25
BUT BEWARE WE HAVE FOUND EXCEPTIONS MAKE SURE YOU CHECK
Triumph
Pre 1980 use 3/8x24 but the new era use M10x1.25
Yamaha
All use M10x1.25
* Brembo fitted as original equipment on Yamaha’s are M10x1.25