Three years later, still having problems with idle

[72degrees]

I am glad that the photos have helped in the identification of your problem, but to confirm without takeing apart just yet though a rebuild sounds in order, do as I suggested in my email to you by confirming the little end is out of kilter. The bush is 17mm and the bore of the gudgeon pin is usually 12mm sofind a rod or wooden dowl thet is a comfortable fit in the bush about 4-6" long insert and then rotae the crank and see if one side touches the crankcase before the other. Idealy a matal rod through the centre of the pin would be better and you could use a 12mm drill to get a more accurate deduction. Having done that the bush should be in the centre of the little end, sticking out equally both sides, the hole in the top of the little end is in the middle of the width of the little end lined up with the forgeing flash mark 7..5mm either side. Lower the rod to it's most bottom and lay a rule or straight edge along the crankcase joint and you should then be able to double check the rod is where it should be in the middle, with a rod through the little end you will be able to determine if the rod is twisted or bent.

Excellent. "Tuning for Speed" is still my go to for checks such as this.

[buzby]

Saunders Engineering in Cadnam is nearby and I can recommend them,

https://www.saunders-motorworks.co.uk/

[harrymuffin]

Tuning for Speed written by Phil Irving who came over before the war and worked for Velocette where he learnt all his pratical knowledge on the twin crankshaft supercharged 500, then after the war did all the design and develpement for Phil Vincent, then went back home to Australia working for Repco and converted the 31/2ltr Buick engine to 3 ltrs by stroking, stuck a single camshaft on each bank and chose the Heron Head combustion chambers where I reckon Lambertini took a leaf from his book and chose the heron head for the trials bikes and then our engines.
In the sixties we had to club together to buy a copy and we revered it. My own copy is falling apart and haven't got it out to read for a long time, every proper motorcyclist should have a copy, even if they are I Phone gruntas with hunch backs and spend all day looking at Arsebook and yawn tube.
Glad to know you admire the knowledge it contains 72degrees, our great minds must think alike!