There are two intersecting spiral oil grooves machined into the small end bush with an oil hole at the top where the grooves intersect...The hole should line up with the slot machined into the conrod...
The gudgeon pin to small end bush fit should not be too close or overheating will be the result...When fitted the piston should fall either way under its own weight with no resistance to movement, yet at the same time there should be absolutely minimal perceptible play between the bush and pin...The bush normally would protrude from either side of the conrod and I see yours doesn't...
If you are going to fit a new big end that would be the time to check the conrod is both straight and not twisted...If handled roughly they are prone to damage when the crank is out of the engine or when the top end is not fitted...Too much force applied when removing a tight gudgeon pin can cause problems as well...Ian
Assuming you are taking about M20 fitment follow the settings and jet sizes for the Monobloc carb used on later M20s as a baseline set up...It should run OK on those settings with only minor adjustments at most...Ian
This is what I have on my M21, works fine.
I mounted a bakelite manifold spacer in order to make the floatbowl go clear of the dynamo drive housing. Think it was specified as for AJS/Matchless, bought a smaller diameter and bored it out to proper size. Might have gotten it from Feked, can't seem to remember.