A7 suddenly running badly!

[Al9000]

My 1960 BSA A7 has started to misbehave at small throttle openings. This happens going from a closed throttle and during the first say 1/4 to 1/2 inch of "twist" if that makes sense. Bike splutters, misfires etc. Will conk out if I stop at a junction on shut throttle.  Absolutely fine with throttle open any wider, in fact it's really sweet.  This happens irrespective of whether the bike is hot or cold and on or off choke.  Running monobloc carb bought new couple years ago from SRM, who incidentally set the bike up ignition and carburration wise on their rolling road dyno this time last year. It's been great up to now. Any ideas where to start looking? I'm a bit of a newbie with tinkering with classics, I've had the bike for several years but my knowledge is very limited.  I always used to call on my big brother for these kind of things as he grew up with them, but sadly he passed away last month unexpectedly.  Any help would be greatly appreciated!!  Thanks,
Al

[BSA_54A10]

Before you do any thing, drain the fuel tank and carby.
put some nice new fresh fuel from your regular supplier in there.
If that makes no difference then try the following

Start the bike on the center stand.
slowly screw the pilot air screw in and out about 1/2 turn.
IF this dose not make a drastic change to the engine speed then  most likely it is a blocked pilot jet.

[Triton Thrasher]

If it's blocked pilot jet be glad it's a Monobloc and not a Concentric.

[bsa- bill]

You have described exactly my problem a couple of months back, turned out to be the cam-ring in the magneto had moved.
Came off it's pin or pin did not have enough hold?, Fixed by FTW as it was under warranty.

Seems that once spinning at speed the magneto will provide a spark via tracking around the slip ring but at slower revs this does not happen

Anyway hope you get to the bottom of it

[Al9000]

Ok thanks chaps, thanks for giving me a starting point and some things to try.  Will post results of my tinkerings this weekend!