Brushcutter Sparkplug

[dax021]

My China brushcutter sparkplug failed the other day, so I replaced it with a NGK equivalent.  When I got home and compared the old and new, I found that the new one had a slightly shorter reach ( approx. 8mm).  Started first go and ran well, but after 15 minutes of use it got so hot that the cheap crap plug lead melted. 

Is it possible that it overheated because the plug is too short and detonation is occurring in that space that should be filled by plug shaft? (hope my description makes sense).  My gut says yes, the heat can't dissipate fast enough like it would if the electrode was protruding into the chamber, so the head is acting like a large heat sink.

Any thoughts, thanks.

[dax021]

Thanks Glort.  I knew I could rely on you for an answer.  I'm hoping to force the lawnmower shop to replace the coil/plug lead seeing as they sold me the wrong plug. (even with the sample I took along)

[dax021]

Pretty much sums it up.  All the above apply this side of the ocean too, especially your last sentence.  I will try, but have almost zero chance of coming right.  Was also thinking of trying to find a car plug cap, something like my old Kombi which had a thread which screwed into the plug lead.