Guy was walking it to the curb. I asked if he was trashing it and he said "yeah, I think it has a bad head gasket, it won't run well." I said I'd take it as a winter project. He said, "have fun." It is a model 917.388521 6.5hp Briggs big wheel walk behind with bagger. I checked the oil. Correct level, just very dark. drained it. Pulled the plug, sooty and dry, replaced it with a spare I had. Checked the air filter...plugged solid with dirt and mouse fur, bedding, etc. I will take a pic for ya. Put in fresh plug, oil, and gas. Two pulls and she's a runner again. Gonna go to Menard's tomorrow and get a new air filter for it. Nice.