I have a 11y/o century 2535. I bought it new and have met or exceeded all of the suggested maintenance. Two years ago, I began to have the following problem: On a hot (in Missouri thats between 90 and105 degrees) day when working the tractor heavily, e.g.brushhogging, for an hour or so, it will began to lose power. It is heat-related because the heat gauge will move from just before the center mark to just after the center mark and will regain power if I open the hood and cool it down. The first time it happened, I thought the radiator screen was plugged. As I was almost done and the problem seemed to be cleared, I smiled re my diagnostic skills a went home. Next time that didn't work and since the sensation was that the tractor was running extremely lean...hence the power loss and heat rise...I suspected the electric fuel lift pump so replaced it.....no help so I relocated the pump as far from the exhaust manifold as possible....no help. So at this point I'm not sure if the heat is causing the power loss or the power loss is from the rise in engine temperature. Other than this heat related problem, I can work the snot out of this little guy with no problem. Any ideas out there????