Popping on overrun, harmful?

I've read everything on here I could, and know it is almost always caused by a lean condition. But my bike will pop everytime at 1 1/2 turns out and doesn't quit popping until they're about 1 turn out. But at 1 turn out the plugs get sooty black. Even with the popping it runs great. I kinda like the sound. I'm wondering what exactly is causing the noise, and is it harmful to the engine? Summary: Is it better to run lean with good looking plugs, or run without popping with black plugs?
THanks,
JD75

popping on let off is famous sound of race tuned engines and does no harm. Sooty plugs implies fuel washing off bores and coke building up so aim for the leaner cleaner plug reading and good response. Slight soot top the thread rims is considered normal but lean burn gasoline tends to lighten the old reading scale some. Proper mixture Commando will need a tickle to start cold and some throttle to warm up, after warmed up but not total cooled off, should start with just closed throttle but may have to grab some throttle to stay lit or may not draw enough initial fuel and stall. If stalled that way I usually try one more kick on cracked throttle, if not fire, then need to re-tickle a bit to light off again one kick. Exhaust air leaks also know to do this if its a new condition.

One air turn out implies a bit low float level so could try tiny base line fuel level rise to get air screw closer to 1.5 turn. Anywho sounds like ball park enough so not in much danger to lean burn valves and such.

My experience is that popping on overrun can be caused by a small exhaust leak, such as up on the head at the gasket. I never tried to tune the popping away because I saw what the problem was (by soot on the threaded collars in one section). Worth a close look around the joint at the head, etc.

Edit: Hobot brought it up, just didn't see that.

No sweat WhitWorth, I can hardly read my own stuff either w/o blurring out. One thing may or may not help leaks is use of dipped dried layers of Milk of Magnesia instead of silvery anti-sieze that tends to flow away. I quite looking but do remember reading that modified hotted engines tend to pop on lets off so traditional sound of power sports even in 2 strokes I think. My Trixie has a bit annoying rough sound on slow speed let off like in traffic or my driveway that she didn't have prior to my by gosh and by golloy float bumping to get the tichklers to stop flooding for some reason after a re-ring job i just set carbs to side. hmm, maybe Trixie has some header leaks as didn't find my MoM in time so used the silvery stuff on bronze Nolts. Thanks for pointing out a lapse in my own attention I'd over looked to worry with again in seeking the perfection that lurks in all our Commandos, for a time at least. I'm rather pleased with Trixie's board range of throttle use and response so ain't bothered to fine tune further til forced to again.

Found this quoted on hot rod ATV 4 stroke forum.

Popping can be a lean condition that lies between the overlap of the main, pilot and needle.

Click to expand...

A hairline crack in the header or leak at balance tube (if you have one) can cause popping on overrun, more noticable when running the bike harder or with no throttle on big down hills.
Regards Mike

harmfull ? NO , Concentrics ! . How Unusual , :shock: .

maybe try winding out the idle screws , see if it changes note .