[Bubblehead]

On a different thread I described how I started having an intermittent rough engine problem. Last night I removed the magneto cap and ignition wires from the plane to do a thorough inspection and found the insulation on one ignition wire worn through exposing the copper stranded wire below. Apparently this was in a position where it would occasionally get close enough to the airframe to short out instead of firing the spark plug.

Three questions:

1) with only one wire on the cylinder not firing, why did the engine run rough? I can imagine a slight loss of power like in a mag drop test but not the rough running that I experienced.

2) I will replace the ignition harness but until then is there a legal, safe repair to the insulation that can be made?

3) when I replace the harness I'd like to shorten the length of a couple of the leads to make a neater installation and avoid chaffing. Can that be done?

The harness is a Skytronics Aero-lite harness on a Bendix D4LN-2021 Dual mag.

 

[G3i Ignition]

On a different thread I described how I started having an intermittent rough engine problem. Last night I removed the magneto cap and ignition wires from the plane to do a thorough inspection and found the insulation on one ignition wire worn through exposing the copper stranded wire below. Apparently this was in a position where it would occasionally get close enough to the airframe to short out instead of firing the spark plug.

Three questions:

1) with only one wire on the cylinder not firing, why did the engine run rough? I can imagine a slight loss of power like in a mag drop test but not the rough running that I experienced.

2) I will replace the ignition harness but until then is there a legal, safe repair to the insulation that can be made?

3) when I replace the harness I'd like to shorten the length of a couple of the leads to make a neater installation and avoid chaffing. Can that be done?

The harness is a Skytronics Aero-lite harness on a Bendix D4LN-2021 Dual mag.

1) The outer shielding is the same as a ground. To wear through the outer insulation (silicone) to the outer braid, is not usually a problem. Sounds like there is internal wire break down, center core to shielding in more than one ignition lead.
2) To keep the braid from chaffing, Electrical heat shrink or vulcanizing wrap tape works well.
4) Most ignition leads can be terminated to any length at the spark plug end.