Taking a look at a Craftsman YTS4500 lawn tractor with a Kohler Courage SV735S 26 HP for a neighbor. It is surging. I'm going to try and post a video so that you can hear the surging. I immediately thought that it was a fuel issue, so I completely removed the carburetor and cleaned it thoroughly. It's still surging. I tried it without the air filter, thinking that maybe it was clogged. Same thing. It seems to surge much less if I run it at full power. Any suggestions? Thanks!