I tried tuning this thing with that shot TQ on it and gave up. Once I get a carb on it that while not idle at 700 rpm with the primaries fully closed, (the throttle shaft leak is massive) I'll have a better chance at getting this little engine dialed in. Right now the idle is 700 to 1300 depending on how the primary shaft rotates back on let off.
HMMM, referring to the above bolded portion of your comment, Have you
1. Disconnected the throttle cable/ linkages and tested with your hand? try opening and gently letting it close as well as letting it SNAP shut.
2. Verified that the throttle arm is completely returning against the idle stop
3. Check and make sure your choke fast idle cam is not on its first step (or close to it) and completely disengaged.
4. Disconnected the vacuum advance and plug the carb port
5. Checked the timing to make sure it is returning to its initial setting and not "floating" down.
I would do all 5 steps one at a time without reverting. IE: do step 1, then 2, then 3, 4 & 5
I would hate to see you spend $$ on a carb to find the problem was elsewhere
Keep us posted
