I have a 96 LX178 and it will mow fine for about 10 minutes then it acts like it is too rich and bogs down. I put new fuel and plugs in it. I bought it used so no idea how old the gas was. I have tried running it with the gas cap off and observed the fuel filter while operating. The filter fills partially (one teaspoon) gets absorbed in the filter material and new fuel comes through the line. Is the filter suppose to be full? The exhaust is not blue or black while this occurs, but can detect a fuel odor. Can the carb be adjusted or any other ideas? I ran it for 5 minutes before I bought it, should have went for another 5 and I would not be doing this... clean engine and chasis so can assume the previous owner was careful. No hour meter available.