I'm using the Champion W-18 sparkplugs in my unstyled Model B. These were recommended by the John Deere dealer, but after ONE use they are all black and fouled and they look like THIS!! Can you recommend a different sparkplug I can use??
They are probably fouled because your engine has a lot wear on it and isn't running as efficiently as it once used to. Fouling can be caused by incomplete combustion of the fuel, and also by burning oil if it is getting past the rings. You might try the next "hotter" Champion plug - the W-20|
However.... What I recommend is the Autolite 3077. See the shape of the electrodes? These plugs will run hot enough to burn off most of whatever is causing your fouling.
And guess what ELSE??!! The Autolite plugs are a LOT less expensive than the Champion plugs. I'm not saying that these plugs are going to solve your problem COMPLETELY, but I DO believe they will HELP!