Are all B31's tight wire advance?
Tight or slack advance depends on the end plate on the mag. Hope attached helps.
Thanks Ian. Didn't realise it could be either/or on BSA singles. Have been used to Norton singles which are all slack wire advance.
TBH it depends on the owners preference. I had the mags for my M20 and M33 overhauled for slack advance as in my mind its more logical at the handlebar lever. I'm not sure if they left the Factory one way or the other.