Been lurking here since I got my first motorcycle, a 77 CB550F, a few months ago; the manuals have been an amazing help! When I bought my bike, the stock muffler was gone. The stock 4 into 1 headers are still on there. I've been riding it without a muffler for a while and, after taking care of more critical issues, I, my hearing, and the neighbors are ready for a muffler. Problem is, I can't seem to find anything that will fit. The outside diameter at the terminus of the exhaust is 2 1/8" or 5.4mm. The largest aftermarket I'm seeing is 1 3/4" and those are designed to slip over and have a friction fit with the mount holding it in. Am I missing something here? I am very much in the process of learning, so please forgive me if this question is ridiculous.