Ben,
I must have the 18mm head as I already have a D16 Champion plug. This plug seems to run fine however I also have a D21 which is a hotter plug. I have tryed it however the mower was not tuned properly at the time. The points gap was too big and firing to early before top dead centre. I also thing it was running to rich at the time as the plug continually fouled up. I might give it another go as it is running better at the moment. Then again maybe I should leave it. Tell me what you think.
Thanks Ben
