sgkent
Lawn Addict
my gut is electrical. If you replaced the spark plugs, make sure you used a major brand designed for it, and not from an online source known for counterfeit plugs. A thermal problem like that can be anywhere in the electrical system - a bad connection, an intermittent connection in the switch, a defective coil etc.. Myself, I like to chase problems with the following mode. Three things are needed to make an engine run. They are compression, spark, and fuel. One must isolate which the issue is.
For spark, I use my inductive timing light. I observe the pattern of flashing when it is running right and running poorly to see if they are the same.
For compression, there is the compression tester. Problems here can be a simple as a tight valve, or leaking head gasket. Heat causes expansion, tightening or loosening the head with expansion depending on the metals involved.
For fuel, there can be a random piece of dirt that was dislodged when the engine was serviced, that is stuck in a jet. Or, some engines might have a plastic intake manifold that is cracked, and that crack opens up and lets in air. Spraying jus a tiny dash of Berryman's B12 around the carb to manifold gaskets, on the manifold etc., can eliminate a manifold vacuum leak.
Another issue can be a plugged exhaust. Many small engines have a screen at the exhaust. It can carbon and rust up over time and cause pressure to build up in the exhaust until the engine dies. Until all that pressure bleeds off the engine runs worse and worse.
Don't discount any possibility, and know that there can also be multiple issues. That said, I would start with a new set of spark plugs. I only say that because I once got a bad set right before a vacation trip, and the problem did not go away until we put the old plugs back in, which I just still happened to have with us. Lots of people getting burned by counterfeit plugs, or cheap aftermarket brands.
For spark, I use my inductive timing light. I observe the pattern of flashing when it is running right and running poorly to see if they are the same.
For compression, there is the compression tester. Problems here can be a simple as a tight valve, or leaking head gasket. Heat causes expansion, tightening or loosening the head with expansion depending on the metals involved.
For fuel, there can be a random piece of dirt that was dislodged when the engine was serviced, that is stuck in a jet. Or, some engines might have a plastic intake manifold that is cracked, and that crack opens up and lets in air. Spraying jus a tiny dash of Berryman's B12 around the carb to manifold gaskets, on the manifold etc., can eliminate a manifold vacuum leak.
Another issue can be a plugged exhaust. Many small engines have a screen at the exhaust. It can carbon and rust up over time and cause pressure to build up in the exhaust until the engine dies. Until all that pressure bleeds off the engine runs worse and worse.
Don't discount any possibility, and know that there can also be multiple issues. That said, I would start with a new set of spark plugs. I only say that because I once got a bad set right before a vacation trip, and the problem did not go away until we put the old plugs back in, which I just still happened to have with us. Lots of people getting burned by counterfeit plugs, or cheap aftermarket brands.
