Lawnmower not starting when hot??

Hello Lmc82848 - Welcome to MLF!
Check to see if it has a good, strong, consistent spark when this happens. That will help determine whether the coil has a heat soak induced failure.

laser3kw said:

Hello Lmc82848 - Welcome to MLF!
Check to see if it has a good, strong, consistent spark when this happens. That will help determine whether the coil has a heat soak induced failure.

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Could low compression cause it not to start hot?

First, to determine wither it's spart or fuel related. If you remove the air cleaner when it's not starting, shoot a small amount of carb cleaner or starting fuel into the carb and see if it runs a second ot two. If so, that would indicate a fuel issue. Plugged gas tank or anything between it and the carb. Gas cap vent and\or carb. If there is a solenoid on the bottom of the carb, it could be failing. For troubleshooting, remove it and cut off the small internal shaft. Replace later.

Spark issues could be coil, plug, plug wire. Remove the kill wire from the coil and see if it runs. Reattach to stop engine. If it runs disconnected, then there are many electrical devices that could cause it.

Check your valve clearances some times if they’re not way off it will start fine when cold but when hot the valves will not let it start. That’s just a thought