For future reference, always give year, make, engine size and model # when asking questions. We need all of that info to give an informed answer. Sometimes the year can make a difference. The top of the muffler is bolted to the frame – remove the bolt. Where the muffler meets the head pipe is a “hose clamp” type clamp – loosen the bolt. Twist/wiggle and pull the muffler towards the rear of the bike. When you get the muffler off – measure it.