Whatever muffler choice you ultimately decide on, remember that the R65s have a
smaller header pipe diameter than all their bigger Airhead brothers. Some replacement mufflers for the R65
may arrive with reducer rings to make a fit. Not a deal killer but do be aware of this when reading,
"Fits all R65 models".
I got a lucky deal on a pair of gently used EPCO stainless R65-specific mufflers several years ago. The ABC magazine
AirMail listed a pair for sale. Called about them and the Taos NM-based blacksmith told me,
"I'll ship 'em to you. If you like 'em, mail me a check for $125.00." They look like Norton peashooters and the sound is terrific.
If you're not in a big rush, check out the marketplace within the Internet BMW Riders site. You can source all kinds of parts and also place a "wanted" ad. It's a free deal.
http://www.ibmwr.org/