if the bike ran ok at some point but now fouls plugs then it's a reed, intake, crank, etc. leak of some sort. if its' always fouled plugs then it may be jetting. you shouldn't have oil outside of your motor. figure out where it's coming from and fix it. once the leaks are fixed if it still fouls plugs then rejet.
i'm betting you've got a leaky powervalve cover. they tend to warp when the bike gets too hot.
Just going on experience. ONce the Yamalube was gone no more fouling plugs (2) on a 09' YZ 250. No jetting changes. Eitherway, I won't use it again.