k11 backfire

[gazman]

greetings, Ive found that if riding with lots of throttle and then back off fast she will backfire, doesnt happen if I back off slowly. changed the plugs, no differance,ordered a carbtune so will sink throttle bodies soon. Any ideas?

[Inge K.]

Check for broken weld(s) at the ekshaust collector.

Also check the rubber mountings, especially the one under the gearbox......worn, broken mountings is often
the reason to broken welds at the ekshaust collector.

[gazman]

changed that lower mount about a month ago, old one was broken. just checked for exhaust leaks at collector with hose to the ear and BINGO she,s leaking. I,m thinking take it off and mig weld it, or is there a better method? thanks  :riding:

[Inge K.]

I,m thinking take it off and mig weld it, or is there a better method?

Tig won't crack that easily between the weld and material, and you reach a bit better into those tight Places.

[gazman]

Thanks Inge TIG it is :2thumbup:

[Grim]

Also pull the throttle bodies if that doesnt fix it. The boots (BMW calls them bushing) are proned to failing with age. It's likely yours are due if original.