V12 backfire

[HEN3781]

Hi
I would be grateful for some advice please.
I have a backfire on overrun. When I take my foot off the accelerator the revs drop and the car backfires. Also at the moment when I reapply the accelerator again. The really strange thing is when I take my foot of the accelerator the revs drop to Zero, its as if the car stalls but it can not have because its in gear and does appear to still be providing power.
I have always known backfire as unburnt petrol in exhaust. I have been trying all the usual things all be it as a new comer to the V12.
If I run it with the choke on a little it does not backfire as above. Is this because its richer or on choke the revs are a bit higher?

Thanks in advance
Tim

[abowie]

Could be lean. Try it with the choke on and see if it is better.

[MarekH]

Have a read up about how the bypass valves work and whether they may be a contributary factor to your problem.

kind regards
Marek