[NZCOBRA]

Hi an air leak from your header gasket or exhaust will cause poping on overun , lack of cross over (not easy on cobra) and more zig zag baffels down inside of muffler will help remove that de-throttle ugly noise. Get somebody to tune your carb , it shouldn't be that rich , it maybe one or two jet sizes too big or maybe you have your idle air screws too far out, I have had 750 dp on mine for years, there great for that jump on it and go feeling. I would not be worried about having the 650 dp.