OK you have the Thunder Bolt system. So I am assuming the problem is the Green wire that goes to the first coil? If so I would say the the problem is probably the Switch Box. Unfortunately, I'm not aware of any way to test the Switch Box with a meter. Next best thing you can do is to make sure that everything else ....the stator and ignition trigger are reading within specs as far as resistance.
1. Disconnect the two Yellow wires that come from under the flywheel and go to the Regulator/Rectifier. Check for spark on #1. If it has good spark, replace the Regulator/Rectifier. Note: the resistance across the two Yellow wires that come out from under the flywheel is about .6 OHMs. Almost a dead short, but not quite. If no change, reconnect the wires and go on to the next step.
2. Disconnect the Blue and Red wires that come out from under the flywheel. Measure the resistance between the Red wire and ground (engine block), and the Blue wire and ground. On one, you should read between 3250 and 3650 OHMs. On the other, you should read between 2200 and 2400 OHMs. If you have a pair that reads way off, replace the stator. If they are within specs., go on to the next step.
3. Disconnect the Brown wire that comes out from under the flywheel and goes to the Switch Box. Measure between the Brown wire and the White/Black wire on the Switch Box. It should read between 800 - 1400 OHMs. Do the same thing with the White wire and Purple wire that also come out from under the flywheel and go to the Switch Box. They too should read between 800 - 1400 OHMS between the White wire and White/Black wire, and also between the Purple wire and White/Black wire on the Switch Box. If any reading on these wires are out of spec., then the ignition trigger is bad.
If all the items in steps 1 - 3 check out OK, then the Switch Box is probably the culprit.
Make sure all of your ground wires are connected and making good contact. Don't just do a visual check, remove the ground wire and clean it off making sure it has a good connection.