A question to those that know please. 
Trying to balance my K100 with carbtune and numbers 1,2 and 4 cylinders are requiring 1.24-1.5 turns out but the closest I can get no.3 is when the screw is 2.5 turns out and turning out beyond this has no further effect. Does this mean that I possibly have an air leak between throttle body and intake stub on no.3? 
Bike new to me so can’t say if the body sync screws have been altered. There certainly isn’t any paint on them. Bike runs fine, no popping etc, idles at 1000-1100. Should I just leave it as is?
thanks j

Yup - sounds just like what happened to me and I had an air leak in the inlet rubber (the one on top). I replaced the lot - inlet rubbers and inlet manifolds (the ones on the bottom). IIRC it cost me £60 or thereabouts from Motorworks. After I'd changed mine the idle dropped from1100rpm to 800rpm with no other changes, so I then wound it back up to the recommended 960rpm -ish.

Would the top rubbers have any effect? The rubbers between the throttle bodies and block sure. Ridiculously expensive for a piece of rubber. £34 for these and a fiver for the top ones.

It's probably the bottom ones.  You can confirm by spraying some starter fluid or other flammable substance around them.  If the idle increases then that tells you that there's a leak.  Or you can spray some water mist around them and see if the idle decreases.

Did you check valve clearance first?

valve clearances, new timing chain and guides done a couple of weeks back. The bike runs superbly but I like to mess. I’m suspecting the weird buzzy sound or nigh frequency rattle from 2500-3000 rpm is either the alternator drive bearing inside the rear casing or more likely a couple of worn rivets on the output shaft with a worn backlash circlip.
Will keep riding and see what happens. 
I’m busy replacing the fork stanchions on my 75/6 so it will have to wait!