G1 spark comes and goes

[bert100]

I just bought two G1's that have been sitting for a couple years. One of them took about half an hour to get running, but the other one Iv'e been messing with for over a month with little luck. When I got it all the wires to the magneto were fried. I rewired it and replaced the magneto and it would somewhat run. After messing with it I found that it was getting a weak spark if any. Today I replaced the coil and it fired right up and ran "really crappy" for about fifteen minutes, and then no spark again. I am completely lost and I don't know where to go from here. I have a few extra CDI's that I plugged in and still the spark comes and goes. When it will run it doesn't have much power and will barely pull a small hill. I bought these from my work and I was actually the one driving it when the wires lit up. It ran great before, and I thought it would be an easy fix. Please help me if you can. Thanks