Lawnmower Stops When Hot

Loose Parts

• Loose parts can be the cause of an engine stalling when it heats up. This can happen in many ways. As the engine warms up, the metal expands and can interfere with normal functioning where bolts and screws are not tight enough. A miss and stall due to poor fuel and air mixture could be the result of loose carburetor mounting bolts where the intake manifold fastens to the engine block. Popping noises that emit from the engine head as the engine is stalling may indicate loose head bolts. Tightening these parts should allow the engine to run normally.

Exhaust Valve

• Popping noises from the exhaust prior to stalling could indicate a problem with the exhaust valve or valve seat. This will require the replacement of the faulty parts. If you are handy with small engines, you may be able to tear down the engine and fix this problem yourself. Otherwise, the mower will require a professional repair technician. Grass clippings getting trapped in the exhaust port area around the cooling fins typically causes the problem.

Ignition Coil

• The ignition coil is partially responsible for making the engine start on your lawnmower. When there is a burn or break in the coil, the engine will sometimes die and will not be able to start again until the mower cools down. When the coil breaks, a piece of carbon forms at the break and is enough to conduct the needed electricity to start the motor when it is cool. However, the resistance is higher as it warms up, and the carbon is unable to supply enough spark to make the engine fire or continue firing.

Spark Plugs

• The spark plugs in your mower’s engine are vital to the machine’s ability to do its job. When the plugs foul out, it can make the engine run rough or stall completely. If the plugs foul out while you are mowing, it may cause your mower to stop, and it may not start again. This is not necessarily related to the fact that the mower is hot, but instead it relates to the time when the plugs fouled out. You may suspect another temperature-related problem, but often it will be the plugs.