Dealing with a Cub Cadet XT2 with a KT735-3078 engine that, when it heats up, often within 10-30 minutes after starting to mow, starts to surge, sputter, and lose power, sometimes stalling completely. These are the following things I did to this mower, but still have the same issues: replaced plugs twice, adjusted valve clearances to .005 (twice), replaced entire fuel system from tank to carburetor (lines, filter, cutoff valve, fuel pump), ultrasonically cleaned carburetor twice, checked out oil pressure switch (good), checked gas cap and tank line, replaced an properly gapped both ignition coils, checked air vane and all carb linkages for freedom of movement, air filter is clean. This engine runs like a top after starting it up, and has plenty of power, for about 15-20 minutes, then it starts to act up. Only surges when it gets hot, and surges at all throttle speeds. I did not replace the carburetor because I don’t typically see them fail when the engine gets hot. Things I have NOT checked yet is the Smart Choke thermostat, and a possible crack in intake manifold (just checked…manifold not sucking air). I do have a 13.66 volt charge coming into the battery while running, but was thinking it should be around 14.4v. Battery is a 300cca. I am a retired mower mechanic, and have repaired tons of mowers over the years, but this one has got me scratching my head. I would greatly appreciate any insight from the pros here on this blog. I know I’m missing something here, but not sure what. When this engine starts acting up, it starts sputtering like I just choked it to about 75%, with no choke knob. Smart Choke issue? Thank you for any input!
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