Rodney: You can actually see the element is clearly broken. Every one has broken right at the tip of the plug about one coil from the tip. Its funny that they are all broken in the exact same place.
ORIGINAL: carrellh
Exactly which engine do you have?
40 LA
40 FX
Something else?
You should be able to download the manual from
http://www.osengines.com/manuals/index.html
I think the 40LA originally came with the A3 plug. OS recently renamed this plug to #6
I think the 40FX originally came with the #8 plug.
The #8 is a slightly "cooler" plug than the #6. It is possible that switching to a cooler plug will help. As others have written, I think your mixture is too lean for the fuel and plug combination. I use 15% nitro and the #8 plug in my two stroke engine and the plug lasts a long time.
Its a 40 LA.