I trust you guys more about building and troubleshooting than any other group. I have a fellow racer that is racking his brain with this one...

Just rebuilt my 400ex it has ran great and then it became hard to start. It had a really weak spark and now it has lost all spark. I have checked the voltage of the stator (getting 50 v output) and Ignition pick up (getting 0.5 v output) I don't have a peak attachment for my multimeter to check the peak voltage. Also checked everything per the service manual.

I swapped out the Coil, Voltage regulator, and the CDI box with parts off a running 400ex. Checked my tether kill switch too.
Checked the Ohm reading on the stator to ground and it is .90, cleaned all grounds and connections. Checked the Ignition switch. Brand new battery also.

has any one ever had a problem like this???

Any suggestions

Any help you can provide will be greatly appreciated.
Mud

 

Mine gave me some similar problems, then started blowing fuses. Turns out the headlight harness is a weak spot on the EX. The wires rub on the metal sockets, and eventually the insulation wears away. Pull the harness off the front plastics, and look for any damaged wires where they go into the rubber boots, etc. Good luck!!!
J.