Here is a Quote from ahicks in post 2.
"Second, I'd pull the idle adjust screw and squirt some carb cleaner in there while watching the tiny fuel ports by the throttle plate. You should see at least some carb cleaner coming through."
I believe this is still the most likely problem and your not mentioning that this type of procedure was done makes my believe this is still a very likely suspect. It is not easy to make this observation.
I have seen engines with this and bam, trickle changed to spray and the problem was solved.
Last edited by kmeyers; 05-01-2016 at 09:36 AM.