Engine Honda H3011 Riding Mower

The mower recently began losing power and the engine missing after running fine for 30 minutes. I replaced the air filter element, spark plug & removed the spark arrester from near the exhaust pipe tip & it runns for about 45 min. now before losing power and missing. If allowed to sit & cool for an hour, it runs fine again for about 45 min. Is there a second spark arrester between the engine and exhaust pipe as shown in the manual? What else could the problem be?

Spend $ 20 on a red neon tube in line spark tester and fit it to your mower then go mow.
If the tube flashes iregularly when the engine starts playing up and does not flash when you are cranking after it has stopped but still hot then the ignition module is toast & needs replacing.
If you get good strong flashes then it is a different problem.
Give it a go then get back to us