I recently switched from a banshee to a 86 250r. I got it in a box and had to put it back togehter.It had no spark so i took all the headlight and any other wiring that i didnt need off and it fired right up. Every now and then it will lose spark until i unplug all the wiring harness and then it will fire again.Is there any wires o should be looking at that would do this??

 

Sounds like a bad ground, wire broke inline or the CDI just going bad. When it will not spark try the kill switch off then on does it backfire if it does it is your CDI. If you need a wiring diagram I can E-Mail you one>