Repairs Help repairing commercial 22260

[Kansgeo]

I have a 2003 or 2004 commercial lawnboy 22260 which starts up and runs for a while then acts like it runs out of power. If I let it set for two or three minutes it will start up again although reduced RPM. Again it will gradually slow down and run out of power ...can anyone help me Isolate the problem… don't know if it's a carburetor, issue possibly a float… Losing compression… Or plugged muffler ... Possibly reeds...
Are there any easy ways to help me narrow the issue down? Possibly some common problems?
Thanks!

 

[bertsmobile1]

Eliminate them 1 at a time.
Start by removing the muffler.
Then try a secondary fuel tank suspended above the mower connected directly to the carb.
Compression is either there or not there but a crack in the head or piston will get worse as the engine heats up but will cause excesive crankase pressure so on a 4 stroke you look to see if it start uffing & puffing out of the breather.
Runs Ok from the start up then peters out can also be water build up in the float bowl.

A few things to keep you buisy between beers.

 

[Mikel1]

Bert has given you some good advice so I will not add much more.
Have you tried replacing spark plug? Spark seem up to par when this happens?