Perhaps a vacuum leak?? Take some carb cleaner and spray it around the intake ports, carb base, and see if the idle changes doing that. Its the first thing I'd do. May as well check the wiper vacuum line for a leak to?
Yes a vacuum leak will cause what you are describing. Look at all the usual suspects and plug the wiper line just for the test. I had a vacuum wiper motor cause all sorts of evil stuff in the past. Went with electric to get away from it.
1, Carb base
2, Intake manifold: 3 places
3, Intake valve adjustment. Surprise!
4, Exhaust valve adjustment. Surprise #2!
5, Float level, if too low it will lean out and starve under load.
6, Vacuum advance, if it leaks you will have trouble.
This will give you a good start. fix one problem at a time. Keeps the stress level down a bit. Also look at the air filter. If it is blocking the air flow you will have more trouble. Enjoy!
vacuum leak; hadn't thought of that, thank you. i also didn't realize the windshield wipers operated off of engine vacuum.
hopefully it's not valve timing, i haven't looked into how difficult it is to adjust valve timing on these engines, but i hope i don't have to be that intrusive so soon.
