The B50 pages @ parkers classics link is below;
Type muffler in his search box. I contacted him about 9 months ago as it had been a long time. He said, "yes" he was still up and running, but things had been slow. The muffler he had copied is like what was on my tr5mx when I bought it from the triumph shop. They had already removed the one into two set-up. But for me, I did not like it. I had a super trapp and extension done up which has remained on there to this day.
Here's what he had written about the muffler in it's description;
BSA B50 MX muffler megaphone 1971 - 1972
Our Price: $400.00
I have been looking for one of these for over 2 years they are unobtainable
Finally I got one on a 71 B50 MX
I have at great expense had this pipe ( a bit battered) digitally scanned using white light scanning technology.
I was then able to view it in CAD and straighten out the bent bits giving me a full dimension model.
I built a fixture and mandrels , then using the correct gauge tubing created an exact copy.
It has been welded by hand (as originals), A NOS pipe that sold last year for over $420 is indistinguishable and identical.
Pipes are straight through "not for road use" and they sound excellent.
I use on my own restorations refund if not delighted
I must say I have 3 B50 MX and each one is slightly different so may need an "Engineering" tweek when fitted
This is why BSA employed fitters
1973 had a different down pipe bends and different brackets but I also have 1 of these and a TR5MX so i will be making pipes for the 73.
So you can have a nice racing megaphone instead of those large twin chrome pipes.
Our Price: $400.00
Availability:: Usually Ships in 2 to 3 Weeks
Product Code: 1008
Takes that long to make one?
As well, Though I lost my database this was created from due to a digital failure, this video was made up of a bunch of B50's photos I had saved over the years. Maybe you'll find an idea on one of these bikes..?
And finally, I say, I have run one of these back in the old days for quite some time with great results... (in my world)
I mean, the bend on the muffler counteracts the bend at the end of the header to give you a perfectly spaced pipe extending past the shock.
But I know, that's not the kind of thing you are looking for. More like the megaphone above. Just thought it was maybe helpful in this thread if anyone else reads it.