rear cylinder not firing,has good spark (new coils) replaced coil pick ups swapped cdi units no help cleaned carbs checked fuel flow ,ok..checked cam belt timing,,its ok..voltage at battery is 13 volts,wired coils straight to Battery no help there.Is their a Ohm test for the Cdi units? thanks.Can a good Cdi unit send a electrical spike to the other unit since they come off the same power source?