Packing the insides of mufflers?

[rumme]

I took the long baffle/rod out of my muffler on a 80cc engine and cut it all off except for 2" rod and then re-installed it..


shouldnt some type of packing material be inside these mufflers to provide back pressure ? Also, when doing this muffler modification, are you suppose to modify the carberutor or rejet it ? Thnaks