I recently bought a 06 rhino 660 and the previous owner had been having an issue with backfiring through the carb since he bought it. While he had it he had added a slip on pipe to it and a different CDI. I have rebuilt the top end with new piston and rings, valves and valve springs. And I'm still getting the backfire. It has an electric fuel pump on it that one of the previous owners has changed. Today I was looking thought everything I thought I thought may cause the backfire and upon inspiring the diaphram I found what looks like a spot that has gotten hot and melted a little. I was hoping somebody could tell me if they think this area could be the problem or not before I order a new one.