Hello Frank:
My opinion Bing carburator better quality control than BVF. Bing mounted in the last 2 stroke MZ models.
Well, I don´t have personal experence. Cuban people tell me Bing 84 (for 250 and 300 cc. MZ models) work ok and very search (they haven´t free market). Tell me also motorcycle drink less fuel than BVF carburator and the only problem is the rapid wear of the float needle valve
I mounted last year a Bing 53 in my 125 and run ok, also mounted an aftermarket exhaust with more open silencer labyrinth and look like original exhaust. The engine have a bit more of energy but I don´t known percentage exhaust/carburator for this.
Un cordial saludo,
Manuel.