| Author | Message | ||
     4cammer |
At times if I am running my '07 XB9R really hard she will "pop" a few times on fast deceleration. I have little to no drivability issues with this bike, good from idle to redline. I am guessing that this is due to the burning of unspent fuel in the exhaust. Anyone? | ||
| Froggy |
Stock pipe? Stock ECM? No matter what you do, there is gonna be some popping, its just the nature of the beast. | ||
| Hughlysses |
Oddly enough, from everything I've read popping on deceleration is caused by a lean fuel mixture. Under deceleration, the too-lean-to-ignite mixture builds up in the pipes and muffler until it finally becomes rich enough to ignite, causing the "pop". One example of this is my 1983 Honda Ascot VT500FT (water cooled 500cc V-twin). These things are notorious for popping on deceleration, and the reason is evidently that the low-speed jets were set very lean from the factory for emissions reasons. Richening the low-speed jets reduces the amount of popping. | ||
| Mikef5000 |
This is perfectly normal. | ||
| Ft_bstrd |
I have the Race ECM and Race pipe. Mine pops on deceleration. I'm pretty sure it isn't related to being lean. I assume its related to there being less back pressure from the stock pipe. As a result, the slowing of the pistons are causing irregularities in exit pressures with the popping being the equalization of the pressure imbalances. Just my theory. Feel free to disagree in private.  | ||
| Tx05xb12s |
Same deal here...pops a bit on decel...running race pipe/ecm/open airbox | ||
| Chadr81 |
I've got the same thing here. D&D, race ecm, K&N | ||
| Diablobrian |
Some decelleration popping can be attributed to leaks in the exhaust system, some due to a lean condition. I KNOW my bike was tuned very carefully by Hal's but there is still a small amount of popping on decelleration under certain conditions.. Don't sweat a little bit of popping, it is part of these bikes' character. | ||
| 4cammer |
Thanks for the replies fellas- I actually love the sound of the "pops" as they remind me of my long departed very high strung '68 Fairlane. Oh, and it scares the cellphone squawkers next to me at times. | ||
| Tx05xb12s |
I usually make it a point to do a nice first gear roll-on wheelie to redline and then snap the throttle closed as I go by our county courthouse and police department. My race can makes a sweet echo off the buildings around the square. I keep expecting cops to pour out of the doors like when you kick an anthill, but no takers thus far.  | ||
| Punkid8888 |
yea I got 06SX with 9000 and I get very minor popping on decel. every once in a while from high rpm to closed throttle in a low gear I will get a couple loud ones, those are always entertaining. my bike is bone stock except for a cut up air box. I have had the popping since about day one, never really gave it a second thought tho, just ride it like ya stole it, haha | ||
| Al_lighton |
It is perfectly normal. A bone stock Buell has plenty of decel popping, it's just kinda hard to tell because it goes pfft pfft pftt instead of POW POW. Al | ||
| Bombardier |
Could it be the relatively short length of the exhaust that let cold air meet the hot? As kid on the farm we used to cut the exhaust off short on our old cars and poke it out the side like a race car. Loud as hell and used to pop like crazy when downshifting. | ||
| Xl1200r |
Some decelleration popping can be attributed to leaks in the exhaust system, some due to a lean condition. ~~~~~~~~~~~~~~~~~~~~~~~~~~~ As kid on the farm we used to cut the exhaust off short on our old cars and poke it out the side like a race car. Loud as hell and used to pop like crazy when downshifting. ~~~~~~~~~~~~~~~~~~~~~~~~~~~ I assume its related to there being less back pressure from the stock pipe. As a result, the slowing of the pistons are causing irregularities in exit pressures with the popping being the equalization of the pressure imbalances. I'm not sure how leaks in the exhaust system would cause the irregular popping we're talking about. I can see it causing a louder exhaust or s ticking noise, but it's a totally different sound. Short exhuasts mean less back-pressure which means a leaner mixture going into the cylinder. Doesn't really have much to do with pressure irregularities. In fact, exhaust pulses go in and out of the muffler anyways, so this is kind of a null point. I'm afraid it's nothing as exciting as you guys make it out to be. It's an indicator of a lean mixture, which under decel is perfectly normal and expected for some engines, such as ours. | ||
| Luxor |
XB1200r wrote "I'm afraid it's nothing as exciting as you guys make it out to be. It's an indicator of a lean mixture, which under decel is perfectly normal and expected for some engines, such as ours." Yep, just the personality of a 60 year old aircraft derived, air-cooled, pushrod V-Twin. I was at the airfield the other day while an AT6 Texan was taxiing for take-off, and wouldn't you know it, it was popping like crazy when the pilot would decel the throttle after an RPM bump. Very cool sounding if you ask me.  I must be the strange one here, I like it. When I ride very hard and come into a hard corner my bike(9S, race ecm w/pipe) will pop and spit on decel. The bike sounds pissed as hell, and also very cool at the same time. Very reminiscent of a WWII radial engine fighter. | ||
| Madsx |
Mine was due to a leak at the header/can. It looked like this.  As per Kevin I tried anti seize around the fitting and and the decel popping is gone. | ||
| Diablobrian |
exactly what I was talking about | ||
| Xl1200r |
Madsx - I think the leaks in the exhaust can also cause lean mixtures as well (just as a leak in the intake can do the same). Someone will correct me if I'm wrong on that. But a leak in the exhuast is not the primary cause for the popping. The leak causes a lean condition, which causes the popping. Luxor - AT6 trainer, huh? You a pilot at all? That old 600hp P&W is gonna pop like mad at anything resembling sea-level, but it's probably happy as a clam at 20,000 feet ;) | ||
| Blake |
The popping is fuel mixture igniting in the exhaust tract. A leak in the exhaust tract allows fresh air (oxygen) into the mix which allows the fuel to ignite. Happened to me at the track once; a fresh set of header gaskets solved the problem. | ||
| Blake |
I've known lean conditions to cause popping out the intake, not sure about the exhaust. I assumed it was over-richness that caused that. Not sure how fuel could "build up" in the exhaust tract. Interesting issue to ponder. Anyone know for sure? I sure don't. | ||
| Luxor |
Xl1200r: I wish I were a full scale pilot, never enough time or $$$,I do fly R/C helicopters though . My dad works for the Museum of Flight in Olympia, so I am at the field alot. The aircraft that I am talking about isn't really a T6 anymore. Lets just say it looks just like a Zero, it was one of the planes used in the movie Tora, Tora, Tora. And yes, the owner flies her alot. She was converted in Canada. On the popping: It's definatly a lean condition. When I raced stock cars(Nascar NW Tour) we would jet the carb to the sweet spot for any given track, and weather conditions. An optimal jetting would produce a slight blue flame and small popping from the exhaust on decel entering the apex. The exhaust boxes on stock cars are very similar to the exhaust on an XB. Header to Straight to Expansion box to exhaust out the muffler with no real exhaust tip. I have heard the reference about the Thunderstorm being built alot like a nascar motor. Well, that isn't too far off. Alot of the internals remind me of a full race smallblock. (Message edited by luxor on July 16, 2007) | ||
| Dentguy |
Popping on decel is caused from being lean. This does not mean your engine is lean all the time. It can be lean at closed throttle position and not in other positions. | ||
| Ft_bstrd |
So does that mean the popping is coming from the headers where they leave the engine or at the exhaust tip? If the lean condition is caused by a closed throttle decel, how would you correct it? | ||
| Dentguy |
Great question Ft-bstrd. Not sure where exactly it starts in the exhaust. In an engine with a carb you can usually solve the problem by adjusting the air screw. It can adjust mixture to a point from closed throttle through 1/4 open. Since we are fuel injected we would have to adjust the computer. Usually popping starts with exhaust or altitude changes. Including exhaust leaks as someone said creating a lean mixture. | ||
| Jwhite601 |
Mine only does it in the first 5 minutes of riding. Then its fine. I have an open airbox,  Force headers  w/modified stock muffler. And i have Directlink to tune it all in with. Heres a shortclip. http://www.youtube.com/watch?v=KrVUwlKkuow | ||
| Cgocifer |
Funny how everyone has a "scientific" theory about this issue. If it is a lean condition, it's not happening in the cylinders. I've checked my plugs and had it dynoed. I have a Jardine pipe, race ecu, and race filter. Pops like hell on decel just as my custom '65 Chevelle does. Actually, just like most big bore, high performance, push-rod engines with headers. Everything I've read or have been told is that the popping is caused from unburnt fuel igniting in the hot exhaust system. No worries. Just check your plugs for proper color to get an idea about how your air/fuell mixture is. | ||
| Dentguy |
If the "scientific theory" was about my comments, they were not meant to be scientific. They are past experience. I have had a lot of performance bikes and cars that were tuned correctly and didn't pop on decel. If there was unburnt fuel in the exhaust wouldn't it be running rich? Not trying to argue just giving my thoughts. | ||
| Ft_bstrd |
That's the issue. I don't understand how you can have both a lean condition AND have unburned fuel in the exhaust system. It's either one or the other. What if I ran it so rich all the time that there was no way that there would be a lean condition under deceleration and also verified that there were absolutely no leaks anywhere in the exhaust? My question again is what could you do to completely prevent the popping? Do stock exhaust systems pop? If not, what is the difference? | ||
| Dentguy |
Ft-bstrd.....Would that be like swimming in a pool and being dehydrated. Do you have any good pictures? A carb could be too lean at partial throttle from a primary jet too small at the same time being too rich at full throttle from a main jet too large, but you could change those jets and fix that..... I would think if you ran it that rich with no leaks that it wouldn't pop..... I don't know what we could do to prevent the popping since we can't adjust the computer. Direct link may solve it, I don't much about it. Jwhite601 said his didn't pop after 5 minutes and he has direct link. It would be nice to have a dyno and be able to adjust the air/fuel ratio at different throttle positions. Maybe this has already been done?..Direct link? I have stock exhaust and I haven't noticed any popping, but its quiet and I wear ear plugs. Sorry it took so long to respond I am not very good with my computer. | ||
| Tripletrouble |
Forgive me if this is a dumb question but, do these bikes have any sort of secondary air injection? That will cause this popping. Chris |
