Does anyone know why the spark plug keeps expanding after a few usage? I suppose this is normal due to combustion. I gap to .030 for the Champion QL78YC. After a few times out, its now like .040+. Should I regap it back to .030 or leave it? Thanks.
If it is in fact growing as you say, then you've got one hell of a problem with plug end erosion. I would look at your ignitions system if this true. The only ones that I know erode that quick is the multifire plugs on some ficht engines.
This is a Johnson 60 degree eagle 115hp. Its affecting all 4 cylinders. I'd have to double check if its exactly .040 at expansion, but it does expands from .030 where I gap them. Also these are new spark plugs. I just finished breaking in this rebuilt engine, so not sure this is part of the reason. Thanks.
Frankly I have never heard of such a happening and don't have a clue as to its cause so I'm going to back out from commenting and will simply observe what others have to say. However, if it were my engine, I'd want to be sure the timing is correct.
