Well...it has been a while...but I need your help again. Toro Z master 255 model 74208, 1998, Kohler 25hp engine. To begin with the muffler kind of corroded to the point it wasn't connected. Now, gasoline is spitting out of the exhaust ports on one side of the engine. Of course it did catch on fire...that is how I discovered the problem... I removed the cylinder head in question and have it sitting in front of me here on my desk. On the inside of the cylinder head, on the back of one of the rocker arms is a lot of black residue....it is probably about a 1/16th of an inch thick. I'm guessing this has something to do with it. Should I just take the rocker arms out, clean them up, and put the whole thing back together with new gaskets or is there something more sinister involved. I'm not really a mechanic but it looks like the only way gas could escape into the exhaust is if there is something amiss with one of the rocker arms. If anyone can help I would appreciate it.