diagnosing engine smoke
 

One of my neighbors has an old troybilt horse tiller w/7HP Kohler. He says that at low throttle it's got a steady puff of whiteish blue smoke, when it's at full throttle there's no smoke at all.

If it was the carb wouldn't it be more of a blackish smoke? I'm still no engine expert so.... :) Maybe the rings? But wouldn't it smoke all the time? Maybe I can get a free tiller haha!