chamber

My 66cc motor won't hardly run with the stock muffler, when I take it off it runs like a champ. Anyone have bikeberrys expansion chamber with muffler? What do yo think of it? How much louder is a regular expansion chamber?

Just to check, you want an expansion chamber to be around the same volume as the cylinder/head/intake right? If you have an expansion chamber larger than said volume does it lesson the effectiveness of the chamber? Or is this not a concern? I only ask because I stumbled upon an old thread...