New Ron Woods muffler, backfire now

[Donny]

I found a new Ron Woods low pipe racing MZ glasspack muffler, and installed it, pic attached. Lots more power, no stumbling, idles well at ~1200 RPM, and lot more noise. I have the Bing vergasser. Alle is ok except for backfire pop when downshift and coast off-throttle through the new muffler. I think the vergasser needs jet change, possibly too lean on the pilot? No pop with the A2 muuffler before, but much more power now. How do I fix the backfire/pop through the muffler? Anyone done this or similar?

Also, I've never checked the valve adjustment. Could this also be causing the backfire? I know it's hard to diagnose as the possible causes are numerous, but I very much appreciate the advice of the experts here. Danke, Donny

[knut]

look here with your questions (there are many specialist)

[Donny]

Knut, many good specialists here too. I will try the link. The best information I ever recieve is here though.

[knut]

many good specialists here too.

[Donny]

Alles ist jetzt okay! A larger needle jet (2.68) and idle jet (48), then readjusting the Bing mixture screw richer cured it.