I have a snapper that looses power once it gets hot. I have cleaned and adjusted the carb. Replaced/flushed oil. And made sure gas cap is venting. It is a 8hp techumsee. It seems a little hard to start when cold. But one I get it running. It runs great for the first 10 mins or so. Then slowly loses power. I also have noticed that when running the high speed needle nothing ever changes. But it seems to sound and run fine. I just was trying to fine tune it just incase. But nothing happens. Sounds the same no matter all the way in or out. I also removed the inline fuel filter just incase. But that didn't change the power issue. When I hit any thick grass. I have to stop the mower and let it catch up. And seems to take for ever. When blade is not engaged it seems to run ok. But like I said when it gets really warm. The engine just losses power and eventually I park it and kill it. Then I can't start it up. It will fire. And try but it won't run. Until its cooled off..