I have had several go karts and wild weed eaters that i took off the muffler and gained some serious rpm and never has caused a prob with the way they run. I know to some noise is an issue and all but Its not an issue for me. I just welded up a aluminum 1" id header for my bosses 2 cyl ryobi weed eater that he wont give to me no matter how hard I begged him,....... anyway, I noticed that the rpm increased over 1500 more than with a muffler, and at night it sounds and looks wicked with the flames and sound, any feedback appriciated! MIKE