Hi gr8taz nitro,

The DL has that crappy spring to make contact with the metal cap and the spark plug, and in turn then sends the voltage back through the ignition braded shield back to the ignition box. I always solder a wire onto the metal spark plug cap and then solder a round eyelet on the other end and then drill a hole in one of the cylinder fins and use a screw with nut to attach it. This way if the spring is not making good contact the voltage from the plug has a way back to the ignition unit. An intermittent spring contact can be causing what you are describing.

Geppino