Hi Everyone! I have an older (1984-1985) John Deere 210 with a 1 cylinder Kohler 10hp it runs great and idles fine, but it smokes. I removed the air filter and it has some oil on it. I removed the spark plug which is approx. 3 years old and it is dry and has black-gray carbon build up. I did a compression test and it reads 120psi. What would cause this? I thought if it had bad rings it would have low compression, not idle well, and have blow by. Could it be valves? Or is there something else i may be over looking?