I have a problem that I can not figure out. I have a Craftsman GT5000 with a 22 HP Briggs & Stratton ELS OHV engine. This mower will start and run fine, for a while. After a while, (45 minutes or so) of mowing, it will start running really rough and I can hear some spitting and sputtering, and then all of a sudden it will start running fine again. I may do this continuously for the remainder of my mowing session, or it may do this once or twice and then is fine the remainder of the mowing session. When it does this, I can just stop and sit for a minute and it will usually start running fine again. Some history of this engine... I replaced the carb early last year. I was having problems and the Sears repair tech said I needed a new carb, and they wanted to charge me $480 to replace. I purchased one for $100 new and replaced myself. I didn't have any problems right after the replacement. I have replaced both plugs, and that didn't fix it. I have tried loosening the gas cap some to make sure venting is ok, and that didn't fix it. I just can't seem to figure out this problem. Like I said earlier, it will be running fine, and then all of a sudden start running really rough, and then after a few seconds (Anywhere from 10-50 seconds), it will start running fine again. It may do this off and on for the remainder of the mowing session, or it may straighten up and not do it again for the rest of the session. Thanks to anyone in advance for helping me with this problem.

Several possibilities, I would first check the valve lash on both cylinders. This is normal service and is often neglected. It could possibly be an ignition module breaking down when the engine gets hot. The blower housing should also be removed and the cooling fins cleaned out of any accumulated debris that may be restricting cooling. The oil and filter should be changed regularly as old and or contaminated oil could be causing the valves to stick when hot. A dirty air filter, a small amount of water in the fuel, or a leaking head gasket, could also cause this as well.

These are just a few of the things that could contribute to the problem you described. Best of luck

Could be some water in the tank and is only getting picked up after turning or after mowing on an incline which could take a while to get to the engine, from tank, fuel line, carb bowl, then engine, so when it acts up you are mowing on flat level ground. Have a good one. Geo