CJ, I had a problem child with similar problems.
Unfortunately on mine, the problem would change, wasn't consistent..

Steve
https://sites.google.com/site/shoodabenengineering/home rebuilt the carbs and it was definitely better, but something wasn't right.
He helped me trouble shoot over the phone, and neither of us could quite find it.
After a lot of frustration, I trailered it to a National and he looked at it.
5 minutes later he sed, "spark plug wires and boots"...
Did that, and problem solved..
I suspect yours is carbs, but do look at your plug wires..
Ride safe, Ted