I have a problem similar to this with my LX-188. Mine will start fine and mow fine, but then it will act like it's starved for fuel and run very poorly for about 5 or 10 minutes. If I just sit with it gasping for life for a few minutes, it will clear itself and run great for another 10 minutes before it stumbles again for 5 or 10 minutes. It keeps going through these cycles (run great, gasp, run great, gasp), which tells me it's not an ignition or valve problem. Does this sound like a junky carburetor to anyone? Both coils and the fuel pump have been replaced. I've taken the fuel line off and inspected it and it looks fine.
Should the fuel filter always be mostly full? Sometimes mine is completely empty, even after replacing the fuel pump, but whether it's full or empty doesn't seem to match up with how well the engine is running.
Any advice is greatly appreciated!!!