my son has a 07 420 rancher he was riding about a month ago when he ran out of gas so he got a can out of the shop that had diesel in it. when i got home it was smoking, i took the tank off and cleaned it good he has run 2 tanks of gas through it and 4 spark plugs, its still smoking and fouling plugs. Do yall think i need 2 put rings in it or what. the guy at the honda shop said keep riding it, it would clear up. what do yall think