wiring on hammerhead
 

We unplugged the main harness, unplugged kill wire for cdi and had spark. Good spark. My buddy plugged main harness back in to see if ign switch would work,which it didn't. Unplugged main harness but now have no spark. The cdi works on running cart as well as ign coil. I tested the black/red wire from pick up coil and it zapped me. But blue/white wire won't register on my needle type volt meter. We get a spuratic spark but is very light and it doesn't stay firing.

Any ideas?

You have to start at the ign switch and work your way back. I can only assume you have an early 150, please confirm engine and year.