'82 Spectre Coil issues

I finally got my carbs cleaned and running good on my '82 Spectre 750. I ran into a new problem over the last few days. Now, when I'm running along, the tachometer will drop from "X" reading down to zero rpm. I'm cruising at 40 mph no problems, then the tach drops down to zero rpm and I have no power and I'm bogging down. The motor itself is still running when tach reads 0, just low on power, feels rough, and won't accelerate so I suspect it's running on two cylinders when the tach drops off. Eventually after nursing it along (20-30 seconds) the tach starts giving a reading again. When the tach starts working all my power comes back. (Back to running on 4 cylinders?) I think my coils are working intermittently. Has anybody experienced these symptoms? I'm planning on replacing the coils with parts from Z1. I just want to isolate the problem first. Thanks!

Sometimes it runs great through low and mid rpm and drops to zero, or I've had it revving at 9,000 before it drops to zero. It definitely seems to happen in any rpm range, which leads me to believe coil problem. Any thoughts or advice are greatly appreciated.