Bach fire through carb, any thoughts?

[ViR2]

Hi everyone

I've just picked my 911 from mechanic, he has adjusted the carbs all to spec, but 2'nd cylinder carb keeps on popping though air filter when under acceleration or deceleration, or just reving quickly. Every other cylinder is working great, but this one refuses to work properly. Any thoughts? Carbs are zenyth (2.4T euro spec), freshly cleaned and rebuilt. Any thoughts? Maybe valves are set wrong?

Also, car feels a bit sluggish when on low revs... I've added full tank of 98 octane, as the gas in the tank was very old, so maybe this will cure it...

[J P Stein]

Originally Posted by ViR2

Hi everyone

I've just picked my 911 from mechanic, he has adjusted the carbs all to spec, but 2'nd cylinder carb keeps on popping though air filter when under acceleration or deceleration, or just reving quickly. Every other cylinder is working great, but this one refuses to work properly. Any thoughts? Carbs are zenyth (2.4T euro spec), freshly cleaned and rebuilt. Any thoughts? Maybe valves are set wrong?

Also, car feels a bit sluggish when on low revs... I've added full tank of 98 octane, as the gas in the tank was very old, so maybe this will cure it...

That is what's commonly known as a "lean pop". You may have a partially plugged
jet, idle or main, but probably the former.... either that or the that cylinder is just set wrong. IMO, there is no "spec" for tuning carbs.....just a tune that works right
for your engine. If you paid to have this done (a fair assumption) take it back.

[ViR2]

thank you for the input, I'll take it back then. Yes, he said mixture is lean in that cylinder, but for some reason he was not able to make it right...