I'm betting on the "weak spark" side of the house. Have you tried jumping it to your car battery to eliminate the voltage draw-down you're seeing...
I can vouch for the relationship between ignition problems and idle quality. Recently one of the crank position pickup coils on my 1982 Seca 650...
You said the idle settles when you grab the front brake. Is it possible you are actually rolling the throttle backwards a bit when you apply the...
I'm happy to report that after replacing the bad 2-3 pickup coil on my '82 Seca 650 last weekend, it is running better than it has for a long...
What is the normal voltage level on the "signal" circuit to the headlight relay on a Seca 650 once the engine is up and running? I see from the...