Definitely hasn't been run on straight unleaded - I've had this mower for 8 years and have managed to never forget to put oil in the fuel, the same fuel was used for three tanks full in the line trimmer right afterwards. Could this have been caused by the fouled fuel?
Will check the muffler and have a look at the piston over the weekend. Question - if the piston and/or rings are damaged, is it worth/possible to fix it?
