Can a lash adjustment effect exhaust pop?

[bad Chad]

I have been running with the db killer in my Mistral can for a couple years now, for two reasons.  All the Guru's say it provides better fueling when in, and it stops the off throttle popping I would get without it.  The down side for me is it is darn close to stock quiet.   Since I don't like the popping, off throttle, and I do like the idea of it running the best it can, I left it in.

But a few days ago I just couldn't take it any more, I needed some soul sound, so I took it out, and the result, it ran great with very little popping at all!  The only thing I can think of thats changed is I recently checked the lash, and snugged them up a smidge.  Some were at most a couple thousands over, so I brought them back to book spec.  Could that be the cause?   This is a 2v Breva 1100.  It's by no means too loud, it just has a nice deep rumble, that can actually be heard!

[pete roper]

Yes, but chances are within a few hours it will trim itself lean again and the popping will return.

Pete

[pressureangle]

Popping in the exhaust is most often a sign of an air leak somewhere in front of the muffler. Unless your EFI completely shuts off fuel, when you close throttle the mix doesn't always light, and the unburned fuel collects in the pipe. Add a little air, hot carbon or fire from a following combustion event and you get a pop.

There are other possibilities, but they all involve fuel and air.

[Bisbonian]

Yes, but chances are within a few hours it will trim itself lean again and the popping will return.

Pete

This was my experience as well.

[lucky phil]

Popping in the exhaust is most often a sign of an air leak somewhere in front of the muffler. Unless your EFI completely shuts off fuel, when you close throttle the mix doesn't always light, and the unburned fuel collects in the pipe. Add a little air, hot carbon or fire from a following combustion event and you get a pop.

There are other possibilities, but they all involve fuel and air.

Mechanical issues aside popping ( as opposed to backfiring)is more often than not a sign of a weak mixture. A weak mixture burns slower to the point where its still burning when the exhaust valve opens, hence the popping on the overrun. The more free flowing the exhaust the more pronounced, richening it up a little on closed throttle will usually cure it.

Ciao

[redrider]

Every one of mine suffered a drop in low rpm grunt when the baffles/killers were removed. They felt a tad stronger in the last 1000 rpm but I do not live there.

[rocker59]

If no air leaks are present in the headpipes, the most common reason for popping on closed throttle overrun is because of a lean idle mixture.

[kevdog3019]

Every one of mine suffered a drop in low rpm grunt when the baffles/killers were removed. They felt a tad stronger in the last 1000 rpm but I do not live there.

I agree with Red with this statement and my results.  There are trade-offs and sound is yet another.

[redrider]

I did modify the killer for the Benelli. The closed end that faced the incoming exhaust was fly cut open. This really enhanced the quality of sound with no loss down low.(ButtDyno) DynoJet 139hp 93lbft.