carl, you have alot of good tips here.
at the very least i would start with a fresh rebuild of the carb so you know where it stands. when you do the carb make sure to replace the meetering needle to . some times they stick. make sure it's not gummed up. i've used glow fuel to clean the tar like varnish out of old carbs. it really works! however it won't touch the hard stuff . remember, a clean carb is a happy carb, ron