Scag 27 HP Kawi loses power: It is a liquid cool 27 hp kawi, Zero Turn 61" Deck 1. Starts up with no problem 2. It can be on and working just fine all day long with no load. 3. It pushes just fine and strong with no load 4. After a 3-5 min with the blades on it starts to lose power. 5. If I turn blades off... it struggles and it dies. 6. Right after it dies, I can start it up with no problem, work it for another 3 min and starts dying again. 7. I took it to my service dealer 2 times already and first they said the gas tank was dirty so they cleaned it, second time they said the carb was dirty so they cleaned it. 8. After the machine kept on doing the same thing I decided to lay a hand on it. I check the valves, valves are ok ( took the whole block out both sides and valves are fine ) Changed both coils ( No. 1 and No. 2 ) Changed both spark plugs. Now i have noticed that the muffler gets RED HOT. I am assuming the machine starts loosing power because it gets too hot, but what i don't know is what is causing to overheat. ( by the way, the gauge of the temp will not reach the overheating point ). The volt gauge marks 0 when machine on ( right in the middle -10!!!!0!!!!10 ). Any suggestions about what might be wrong with this monster??? I would greatly appreciate any help!!!