Id start with syncing carbs first, using a tool is really the best way to get them perfect at idle. you can get em pretty close with out it, but syncing them at idle is with a tool is best. like mull said cleaning carbs and syncing would be a good place to start.
https://www.amazon.com/Latest-Rage-Deluxe-Carburetor-Airflow/dp/B00CMC57R0/ref=sr_1_4?ie=UTF8&qid=1507940497&sr=8-4&keywords=carb+sync+tool
-how I usually rule out an electrical problem is I will first trim back the wires on the secondary leads so the are fresh
-then ohm test all electrical components with multi meter (stator, coil, plug caps etc) check wireharness.
are you just breaking this motor in?