Chuck, as usual you are correct that there was one size originally. But, many parts suppliers list a 38mm muffler for conversions. I have two here in the box, one that fits and one does not. They shipped one of the wrong size. That’s why I mentioned it to be sure people get the right one.sherman980 wrote: ↑Fri Oct 22, 2021 11:43 amJay,
I believe you are mistaken. In over 40 years of playing with 50's and 60's era BMWs, I have NEVER seen anything other than 36mm OD exhaust pipes for R51/2 thru R69S bikes. Given the factory machined exhaust port on R68, R69 and R69S heads is 36mm ID, I'm not sure how you could install a 38mm or a 40mm exhaust header unless you bored out the port and modified the clamp ring assembly and finned nut to accommodate the larger diameter. (38mm OD pipes were used on /5 era bikes and 38mm and 40mm OD exhaust pipes were used on /6 era machines.) Please remove your post before it becomes another "internet fact". Too much of that out there already. Not trying to be rude, just hoping to convey correct info.
Also, the only non 36mm inlet mufflers for this era bike that I am aware of are those made specifically for conversion bikes that use a /5 or /6 engine and associated header assembly.
Thanks.
Chuck S.
I mentioned it because it’s something we need to know about and I am still waiting for my correct left side muffler!
I edited my original post to ensure I specified that as well.