I have an older model kohler comand 18 hp unit on my 61' scag Hydro. If I had to guess the engine is from the mid to early 90s. I purchsed this unit used last fall, and don't know the complete history on it. I have noticed that on occasion there seems to be an accesive amount of oil comming up through the air filter. This does not happen all the time, but I have noticed it on occasion ( of course any amount of oil in the air filter is wrong) Anyone have any ideas on where I should start to look for the problem?