Small Engines (Lawn Mowers, etc.): quiet down a Briggs exhaust, deer camp, flex tube

Question
 My father and I have a deer camp in northern Michigan where we run a generator for power. To try to keep it as quiet as possible we tried to run a straight pipe from the exhaust port to a piece of 2 1/2 inch x 6 foot(automotive) flex tube and attached a car muffler. This did quiet the motor but after a few hours (5or6) of running it started acting up. Is this becauase the tubing is trapping heat too close to the engine? Is there a better way to quiet it?

                            Thanks!  

Answer
Hey Aaron,
Im not quite sure that there is a better way. The way that you modified it does sound really good. If i were you I would move the muffler closer to the engine because the heat might melt the welds and cause holes. Also if you welded the pipes make sure that you keep puting layers of weldings to make sure you patch every hole. If you havent welded anything than weld the joints this will silence the exhaust sound. Hope this helps.