Odd Plug Carbon

[Bart_]

I was picking away at small dead scruff all velcroed together today with a small 2t polesaw keeping the revs down to avoid kicks and entanglement. Turned the saw off for fuel and it wouldn't restart. Figured hot, maybe winter gas vapour lock, maybe grit in carb no fuel, it wouldn't fire normal, choke or wot. So out comes the plug. Bit moist maybe at a stretch, but then I saw 7/8 of the way around the plug it nearer white than normal but in one spot looking at the side of the ground electrode was a little strip of black down the side of the ceramic that looked curdled like paint wetted with paint stripper. Weird. Came off real easy with the dental pick, motor re-fired first pull. Never seen carbon behave like that before.

 

[The Green One]

I was picking away at small dead scruff all velcroed together today with a small 2t polesaw keeping the revs down to avoid kicks and entanglement. Turned the saw off for fuel and it wouldn't restart. Figured hot, maybe winter gas vapour lock, maybe grit in carb no fuel, it wouldn't fire normal, choke or wot. So out comes the plug. Bit moist maybe at a stretch, but then I saw 7/8 of the way around the plug it nearer white than normal but in one spot looking at the side of the ground electrode was a little strip of black down the side of the ceramic that looked curdled like paint wetted with paint stripper. Weird. Came off real easy with the dental pick, motor re-fired first pull. Never seen carbon behave like that before.

Interesting find Bart.

I have found "Carbon Tracks" on the outside of a plug ceramic, but your inside carbon track is a new one for me too.

I wonder if there is a defect inside that plug. I'm sure you will keep an eye on that and have a spare plug on hand for the next time IF it happens again.

Very interesting!

 

[Bart_]

Ran the same machine again on the same fuel mix doing the same task - this time I didn't try to restart it. Exact same plug condition same spot on the porcelain except the black region was a relatively thin layer, smooth shiny black. I think it didn't orange peel because it wasn't exposed to a bunch of wet gas during failed restarts. And it was running fine with what seems like a carbon shorted plug. Ran this actual plug for years mostly problem free - the odd gooey chunky carbon foul from cedar trimming but this is different.

I didn't do the restart fight, I just cleaned it and put it away.

Go figure. ?