A trick I learnt very recently when repacking the muffler on the Team TART RM80 in preparation for the Classic (thanks Foxy) was to "bend" the perforations in the muffler tube so they face into the exhaust gas flow. Along with not packing the muffler too tightly (already mentioned here), I found this to be the best single thing I did to the massive 8 inch muffler. It really worked.
I don’t consider that advisable.
Curling the perforations into the flow will only force the exhaust gases into the muffler packing part of the muffler.
As the gases find a way out again they will take a little bit of packing with it eventually blowing all the packing out making the bike louder and giving a drop in performance.
Once the perforated tube is wrapped with packing it simulates a ‘normal’ tube which gives the best performance.
Once the packing starts to disappear the gases find their way into the packing area and out again creating turbulence in the exhaust gases as it tries to leave the muffler, I believe this is why a power drop is experienced and why it is recommended to keep the muffler packed.
I normally wrap my mufflers moderately tight.
You don’t want the packing so loose that the exhaust gases can start to filter through the perforated tube as it starts the process of blowing the packing out.
