bitzer
******** Timber Expert
I get bark to the point that it is smoldering all the time with my 440. dont look like it was "heat blistered" to me, never heard that term before when talking about a spark plug, color looks typical to me. not lean and not hot.
I believe it, just never seen it actually light. Heres a spark plug chart that mentions blistered on the overheated plug. The picture is not great, but there are several other charts if you search online that mention blistering. Don't know how common this would be in chainsaws though. Just my thoughts.
I don't think ethanol would be a major contributor to this, but it definetely wouldn't help anything.