I have had this rider mower for 9 years. Always kept inside. No corrosion. Well serviced and maintained. Has always started and run without problems. A month ago it stopped after running for about 20 minutes and it continued to do this, only running 15 or twenty minutes and then stopping as though it had run out of gas, and starting again easily after sitting for a few minutes. I changed gas, replaced fuel line and filter, spark plug and ignition coil without success. Finally installed new carburetor and have not had the problem since. For my own information, can anyone tell me what could have been wrong with the carburator that would have caused this? The engine is a B & S model 310707 type 0137-E1 and it had a nikki carburetor.