17hp Simplicity liquid cooled loses power after running for an hour. If I pull out the choke it will keep running. Also when the grass is thicker it will bog down and start to miss. I put cleaner in and it help a little. I also pulled the float bow and there was no dirt what so ever. Checked fuel line for cracks along with pulling line in fuel tank. I also looked at the fuel pump and it works fine.
Post your Simplicity 7 digit model number please. Check air filter, spark plug, as well as oil & filter for replacement. If your tractor is more than 3 years old I am suggesting you remove and clean blower housing & screen on top of engine. Disconnect negative cable from battery for safety. Did this today on my 2010 Simplicity, it's a dirty job but needs to be done so engine can breathe and run efficiently & cooler. Clean cooling fins above flywheel, I used a small paint brush between fins, also remove as much crud as possible at heads, etc. Be sure you have a roll of shop towels or rags. This is very time consuming so be patient and take your time, reminds me of a doctor performing surgery. Use you judgement as far as tools to use goes, I used a pocket screwdriver for hard to get to places. I used compressed air with blower nozzle after loosening all the crud up. Let us know how it goes.
