I forgot to mention the cdi on my bike is about a year old. I didn't replace it when I put the new motor on.
So I took it off and installed a different one. This one is used too, but known good. After installing it I went for a ride. It started up fast, and seemed to run a little better than before, especially when cold. After 3 cold starts my impression is it seems to run better than before during warm up. Full hot operation seems the same as before. I've put about 10 miles on it since I changed the cdi, and it hasn't had a problem yet.
The problem is, I changed the spark plug at the same time. When I looked at the stock chinese spark plug, it already showed signs of wear in only 200 miles. I installed a new BP6HS, so that could account for running differently during warm up.
There's not much to the wiring. The ends of all the wires are soldered, but not together. They're connected with 2 wire nuts, and a wire tie. I like it that way because it's easy to work on, but normally I never have to.
I checked the kill switch. There's no continuity to ground, and when you push the button, the switch goes to zero ohm. I don't think the switch has a problem.
I ohmed the magneto coil cold @ 36 ohm. I guess a coil could have a intermittent short that only shows up when it's hot. If the cdi doesn't fix it, that's the next part I'll replace. This magneto is the new one that came with the motor.
There's no white wire.
I'm optimistic it's fixed now, but a little paranoid to get very far from home. That won't last long if keeps running though, because I like to ride the range.
I'm going through the third gallon now @ 22:1. So far I've been breaking it in on Torco synthetic 2 stroke oil. I know you're not supposed to, but it's been over 100 degrees everyday. I'm going to bump it up to 34:1 on the next gallon or two, and after that I'll probably go back to 40:1 red line synthetic. These are both premium synthetics, so I expect breakin to take a long time.