Jim,
The Power Dynamo system is well liked, but I vote for making a stab at the orig. set up before giving up.
I got a Gilera 106cc working well. It took time, but vintage machines are a joy.
Before replacing parts, take a multimeter and check;
1. Grounds are good, where parts should be grounded
2. Parts are insulated, where they should be insulated.
For example, my Gilera had no spark, and I found that the ignition coil was grounding to the points plate, and then to the frame. I re-wound the coil manually, and then insulated the plate. Blue spark now!
Radio Shack (a store of the past?) was great. They actually had "magnet wire" in stock on the shelf! This is the wire to re-wind coils. There's no other common store that keeps that in stock. Best Buy, etc? Those supposed electronic stores just give you a funny look when you ask for magnet wire, or a condenser, et al.
The small Italian bikes had electrical systems similar to vintage mopeds, so look at it that way. There's support from moped sites (Moped Army), and Yahoo Groups has several groups dedicated to small Euro bikes. Yahoo Groups is especially good, because they're made up of older men who understand vintage cycle repair.
There's one or two excellent books on moped repair (Safe Moped Oper and Repair, Neil Schultz; Moped Repair Handbook, Paul Dempsey), as well as the usual books of that era on repairing motorcycles (Troubleshooting Motorcycle Carb and Electrical, Clymer, 1976, Motorcycle Electrical Systems, Chilton, 1969).
Please keep me posted w your progress,
Joe
