did you try another spark plug ??..if so..then your best bet..replace the c.d.i., but..before you go do that..check all your wires..connections..ground leads..switches..make sure they all are ok..if so..then replace the c.d.i.I have a 400 ex and it will not spark. I have replaced the stator, ignition coil, plug and plug wire. I have checked the plug wire and no spark. Anyone have any advice??