Backfiring and Decel Pop - Is It Bad For Your Motorcycle? | The Shop Manual
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As motorcyclists, our bike’s exhaust noise is a source of joy, pride, and… concern? People sometimes wonder whether decel pops and backfires are an exciting anomaly or something to be worried about. In this episode of The Shop Manual, Ari explores the difference between decel pop and backfires, and more importantly, explains which one is normal and which one means there’s something wrong with your motorcycle.
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Which exact knife are you using at the open?
@@KutWrite🎉🎉😂🎉😢🎉😮🎉😢🎉😢😢😮
I’ve got a Triumph Speed Twin 900 and occasionally on engine braking, it has started to pop really loudly…(note for later)
I was coming into a corner decelerating from Mach Jesus and downshifting when I picked my corner gear and I heard a loud bang from the exhaust.
Today I heard a loud pop when decelerating in a higher gear but at a lower speed.
Decel pop is better than k-pop
Emotional damage 😂😂😂
Amen
False
Both… both is good
Amen
Glad you mentioned the correct definition of "backfire". One real backfire can bring everything to a halt.
Indeed! I had the throttle body blow off a Husqvarna out in the woods once. It was quite a surprise!
@@Seven-yg2srthose were wild. Had a TC610 quite the ride. A lot of power :-)
I JUST installed an aftermarket exhaust a few days ago and was surprised by the decel pops that began after. This video was timed perfectly as I was wondering if that was a normal thing! Thanks Ari!
Shorter exhaust baffles allow oxygen back into the exhaust system due to camshaft overlap which can cause afterfire.
It means your bike needs to be tuned to work with the exhaust you've installed. You likely now have a lean stumble off the bottom too.
It's very normal with an aftermarket exhaust, usually when the bike is cold, you not need retuning or mapping unless it's really bad. As he says in this video "decel pops are normal and nothing to worry about".
@@flippy66They normally occur when installing an aftermarket exhaust. They always disappear when the machine is tuned properly.
Convincing people it is normal, makes it easier to sell exhausts; as does convincing people it sounds cool.
I put a danmoto exhaust on my bandit, and the decel pops are amazing.
Roll down a hill with barely any throttle input and it goes popopopopopop the whole way down. Really makes my inner child smile.
Have you checked the plugs to see if it's running lean? I just got a bandit with full exhaust and she pops like a mf. Gonna pull a plug and see how it's looking in the next few days but it does sound awesome
@flatman When you install a higher flowing performance exhaust system, you must also re-jet the carburetor(s), or reprogram for EFI fuel systems.
You need to richen the air/fuel mixture to compensate for the added flow of the larger pipe, otherwise the engine will run lean.
IMO, the explanation given in this video did not put enough focus on how increasing air flow with a performance exhaust, and/or modifying the air intake, will almost certainly disrupt the air/fuel mixture, causing a lean condition.
Some of the main symptoms of a lean condition are, hard cold starting, popping on deceleration, higher engine temps, random stalling, poor throttle response/hesitation (especially off idle), and premature engine wear/failure.
This video has put my mind at rest after installing a slip on to my bike. I was getting popping sounds and grumbling when rolling off the throttle. Thanks!
Bought my R1 already tuned, after 2 and a half years I've got my AIS (pops & bangs) turned back on. I don't see myself getting tired of them 😂
Great video.. I think most people get decel pops confused with lean pops and worry unnecessarily. Back in the day with carbs and simple EFI systems when you'd put a new exhaust on it would lean out your mixture causing the bike to run super lean and pop on decel (which was bad back then).... newer bikes are popping because of what Ari was saying...from fresh air being injected into the hot exhaust gas...so it's totally fine now.
Most newer bikes are already running incredibly lean from the factory should still get a tune if you change your exhaust or intake especially is you do both.
@@milodudeful yeah they are way too lean. I agree with its mandatory to get a tune if you do air filter and exhaust. But since most of bikes restrictions are from the cat and breadbox resonators..just doing a slipon doesnt really do anything anymore. But getting a tune is always a good idea..these emissions regulations are pointless and in some cases cause more pollution.
@@JeremiahHartmanPhotography Oh ya I see what your were saying now. Ya if you're just doing a slip-on you don't need a tune. Honestly kinda forgot about slip ons cause mine stone was one welded piece so I needed a full exhaust lol.
Oh yes, I have a simple carbureted bike, and one day it started popping like crazy on decel. That's how it told me the ignition coil was going bad lol, so I replaced it and boom, like new.
@@Jayui22 wow and how did you figure out it was the ignition coil? is it a common sympton?
Thanks for this. I did a lot of research and came across info stating decel pops are caused by being lean. However, your explanation of having a high flowing aftermarket exhuast with no cat makes more sense considering a 2 into 1 has a lot of scavenging and no restriction.
Great explanation and video as always! I thoroughly enjoy watching your videos and have been viewing them for years! You have always been a great help! Thanks!
Glad to see you recovered well from your accident.❤
Ive had this argument with a few people. Youve also cleared up another argument Ive had about backfire and afterfire.
Thanks for this vid. I've gone from a leaky manifold that was causing backfires to a fresh full black widow system on my carb blackbird. But I have been noticing backfires when I'm rolling down the revs. After this vid I'm convinced it's audible decel pops as they're quiet and in line with the audio clip. Thanks for putting my mind at ease. Keep up the great vids
Can anyone please tell me why does bikes like ducati or any supersport motorcycle produce a loud bang on quick shifting at high rpms ?? I am assuming that it is because the engine is taken away from one or more powerstrokes cuz of quick shifter , so to compensate the drag caused by the no powerstroke cycles , it pumps more fuel and air in the immediate powerstroke ??
Hi Ari and greetings from Greece!! I love your videos and I learn a lot all of those years from you!!! I would love to watch a video of you, to explain what is the trail and the caster angle and if it is factor to choose one bike from an other. ( I am not very good in English so I hope to make sense 😅)
learned something new today , always thought that the they were the same thing, first time hearing the word decel pop in my entire life as well. I just installed an aftermarket pipe in my bike and some of my mates would tell me that my bike was backfiring , but thanks to this video i now know the diff of the two. great video as always!
Now you know!
Thanks to your video I now know what causes backfiring and could instantly fix it on my bike by setting the needle one step richer. Engine runs cooler now aswell.
Dude. So good. Love that you actually explain/clarify the misnomer of the afterfire "backfire"
Great video as always.
I'm literally battling this right now.
So happy this came out today ! Thank you so much for the vid !
When I fitted a SP race can on my ZX9R c2, it constantly popped on decel, so I turned the fuel screws out a 1/4 turn, still get a slight popping, but not as bad, but I also removed the klean air system!
Thanks so much. This is really helpful!
Rock solid basics, well done Ari! You have a knack for picking subjects that have needed clarification for decades!
Thanks for the compliment. Can you think of any other topics we should cover? We're always looking for suggestions and ideas.
@@AriH211 Could you do a video on the differences between stock vs aftermarket headers? Once the Cat is removed, would the headers from a full race system even make a difference?
@@AriH211Can anyone please tell me why does bikes like ducati or any supersport motorcycle produce a loud bang on quick shifting at high rpms ?? I am assuming that it is because the engine is taken away from one or more powerstrokes cuz of quick shifter , so to compensate the drag caused by the no powerstroke cycles , it pumps more fuel and air in the immediate powerstroke ??
Bro, you started making video again ?? Glad to see you !
I have a ducati streetfighter 848 with full open Termignoni slip ons. Was professionally tuned. Pops and bangs (like a shotgun) constantly when off the throttle. Also when using quick shifter will pop on the up shift, especially when not warmed up fully(with a nice blue flame). Great video(as always)Pity not more audio examples.
I have the same bike, and the same slip ons. Downloading the TuneECU app and buying the adapter is a good idea. The Termignoni slip on map or the DP map and uploading it is worth a shot. Both eliminated the decel pop entirely and eliminated the dead spot below 5k for me.
Years of riding and I had no idea. Thanks TSM
My Yamaha had an AIS (air injection system). Installing after market slip-on exhausts made the bike pop like crazy on deceleration after tuning and syncing. Removed the AIS system since I didn’t need the extra air with the more breathable exhausts and no more pop occurred. It was more so an emissions thing.
one should perhaps differentiate with the Backfire: too big or no DB killer (bad for the rear silencer) or too short Header (bad for the exhaust valves). In both cases, fresh air is announced through the Muffler and ignites unburned exhaust residues. but if it just pops out the back, it will damage the insulating wool in the exhaust at most. However, if this mixture explodes up to the exhaust valves, it can hurl them back against the valve springs into the combustion chamber or at least cause a second hot flame front on the valve disk
my monster 1200R was having a lot of decel pop with a SC project slip on. After a tune, cleaned fuel injectors and removal of the secondary air system they are pretty much gone.
Did you choose a CB500 on purpose on or was it simply coincidence? I love the burbles and pops that my CB500X makes on the overrun through its standard pipe.
Good stuff Ari. Thank you!
Ever so informative, great video Ari
Great explanation, thanks 👍
Nice concise explanation of the difference - thanks again.
You're welcome!
Thoroughly enjoying watching this. I didn't understand what was going on when those two dial test indicators were being used on either side of that shaft sat in v blocks and then the counterweights were being struck it was being struck with a mallet. I don't understand how that brought the readings to zero.
My SC Project pipe is still fully noise compliant, but it's pops off the throttle are absolutely musical compared to stock, without being obnoxious.
Not so much tinkering on this episode, yet very well informed ! Keep up the brilliant work !
it means you need to turn the airscrew in or change to bigger jets. After making sure the float Hight is correct in the carb. also blocked carb jets can do it
Hallelujah for this video. A question we get everyday and I will point people to this video for an explanation. Good job Ari
I remember watching Ari Henning at the MC Garage when I got my GSXR 600 6 years ago. I just bought a brand new 2023 Vulcan S and now I'm taking his advice at the Shop Manuel. The advice from both the MC Garage and the Shop Manuel have kept me smooth as a rider. Thank you Ari.
Who is manuel
@@checkyourself164 manual. That was my spelling error lol
Perfect as always... ❤
Been meaning to get a carb jetting kit, finally ordered now
Thank you for this information
Refreshing to see someone who knows what a backfire actually is. I love that he briefly mentioned off-throttle fueling as well. From the factory for emissions reasons, when you close the throttle completely you get whats known as decel fuel cut. When transitioning back to on the throttle and starting fueling abruptly again, this causes a harsh jerking transition. Any proper flash tune (not piggy-back trash like power commanders) can disable this. The downside (or upside depending on you) is angry demons releasing from your exhaust on decel, with potential for flames depending on your exhaust setup. The off to on throttle transition is 100 times better with this fuel cut disabled.
Side note, cars and trucks do this as well. Its not as noticeable of a transition as on a bike, but it still makes a wonderful difference when disabled.
Hi, any downside with turning off this option?
@@MRsickcat84 None whatsoever from a reliability or driveability standpoint. Enjoy the better driveability. Your emissions will go up by a minute amount.
@@Dexter-tx5fp great! Thanks man!!
Awesome video and explanation!
This series is a great idea!
Thank you for talking about the difference between after fire and back fire!
I love Decel Pop!! Love it. On downhill bends I laugh and cheer like a madman!!!😊 Scramble on!!
Thanks. I never knew that the perforated screen on my air cleaner was a flame arrestor. Also, at least on GSXR's, it's fairly common to remove the air injection system when an aftermarket exhaust is installed. PAIR blockoff plates are sold for that. That moves the flames to the back of the muffler and lessens the sound.
Would you say it’s required to get block off plates when installing an aftermarket exhaust?
Not required but, unless you're an exhibitionist, the popping will be quite annoying. It will stress the packing in your pricey new muffler until it fails prematurely. It will also screw up the air-fuel ratio as indicated by the exhaust, making it impossible to dynotune the bike (it could be temporarily blocked for the tune).
The CBR500R in the video is a perfect example of this. Bone stock they pop like crazy including mine because of the PAIR valves. Great video
Love my cb500f. Received several compliments regarding sound at some red lights
I have n FZ1, and when I put on a different exhaust system the popping on the overrun was very audible - it did concern me initially, but learning how the PAIR system worked I understood it was nothing to worry about. On a stock exhaust or with the baffle in the current exhaust, the pops are not easily audible, if at all. I can take or leave it, but my father says it sounds very cool!
It seems to be a pretty common thing, my SV 650 also has a PAIR system. I wouldn't be surprised if it was linked to the Euro regulations.
Please more I need them!!
I can program in developing pop and some flames with my tuner, it’s a fun trick to shoot some blue flames once you get the hang of how to make it happen.
Thank you for this info mate. My XR500R head bolts are stripped x3 and when the bike is cold it runs smooth but when it heats up it back fires. Your video helped me understand that is could be compression loss causing the pop. I'll get my bike sorted next week.
I would love an episode on electrics... Voltages to be precise. At what voltage is your battery charging or discharging... When are you in trouble? How can you tell how full the battery is? How do you know if your battery is dying or your regulator is failing? So many questions! 😅
Hello, I have a question. I have a Honda CBR 500R 2016 and I was wondering if it is bad to shoot the exhaust with the kill switch?
My Triumph Speed triple 1050 has the decal pop as standard i love it.
Good presentation. Anytime you open up your exhaust, you must richen the mixture of carb or EFI, or your bike will run hotter. I took the absurd Cat of my bike and installed the Booster Box. Idles better, off the line better, accelerate better and sounds better. If it pops I can't hear it on the bike. It's only louder when you dial it on. But I did notice a few weeks back, a few threads of fiberglass hanging out the back. Haven't seen any since. Meh.
Love these videos guys! If you haven’t done one yet, I would love to see you all tackle the myth or truth of “backpressure”
Dun
Dunn
Dunnnnn
I love my MRD decel pop on DRZ
'85/'86 Honda Shadows were notorious for decel pops. I seem to recall Honda stopped making them for a few years before coming back with a completely different style with no decel pop; but according to Wikipedia they kept making them from '87 onwards, albeit with the different style. Weird.
I had my Ducati monster tuned and all it did was dump even more fuel to already rich airhead. The decel pops were fun....for a while. Still get the odd airhead trait of airbox vacuum pop (infamous on old boschtronic Porsches)
I have a CB350, and it's almost a year old. But almost from factory, engaging into first has always been a mess. Quite tight, loud noises and would jerk the bike forwards a bit, and would sometimes would just return back to neutral. The showroom said it was due to the auto choke pulling up idle revs on first startup, and it was completely normal. But it occurs always, not just during first startup. I've made it a habit to just start the bike in gear with clutch engaged. Is it bad to do that? And what might be the problem causing the noises during first gear engagement.
my snowblower pops when the throttle goes from full to low all at once. and it’s extremely loud.
i’ve had it for years and runs great.
starts every season with no issues.
has never blown up.
another great Ari video.
Accidentally installed my 1973 CB500 cam 180° out once. The result was true backfiring.
This video is really important for a lot of people, both car and motorcycle enthusiasts who love to do burble tunes just to get the "cool" backfires and flames from the exhaust. Probably one of the worst tunes you can ever do.
remove/block the pair valve to get less or even completley eliminate pops
best explanation!
It can be as simple as a leaky exhaust: My old (old? ANCIENT!) Ducati Paso 750 starts to backfire when one or more of the blindrivets holding the muffler together is missing. Strangely, it does NOT backfire if the connection between header and muffler is leaking, only when the rivets are missing.
Never heard it backfire on a dirty or poorly adjusted carb. The Honda CB400T I had before it (end 80's, early 90's) did the same: Backfiring on a leaky exhaust.
Love the shop manual!
yep
my cbr150r has the backfire after i install aftermarket exhaust on it
the power loss at 4k-6k rpm is noticable but the bike ran better at higher rpm range 7k-11k
this happened because i didn't tune the bike yet
but my buddy bike have the same system but tuned
he didn't have any backfire but more pronounced decel pop also don't suffer power loss at 4k-6k rpm
and better acceleration at 7k-11k rpm range
-
tune your machine, if you can't afford to tune yet maybe it's not a good idea to put aftermarket exhaust on the perfectly fine machine
mine has only 30k/km on odo but suffer the valve clearance issue while my buddy bike didn't even tho he has the aftermarket exhaust on.
My 650R (bone stock) burbles VERY nicely whenever I ease off the power. It's not very loud, but it's there, it's noticeable and it sounds good to me ;)
Great video as usual! I just wish you would've included shift pops too. Just like decel pops on most cases shift pops are fine too as long as it's just 1 pop the moment you shifted your gear (mostly on upshift when you close throttle to rev match, so a bit of fuel remained unburnt and it popped in the exhaust). And in most bikes this will completely disappear with fueling adjustment.
Was curious about this. I get some shift pops occasionally after riding around for a long time at low speeds or being stuck at a light for a long time. Glad to hear a single pop isn’t a big deal, and assume it’s a build-up of fuel considering when it happens for me?
@@Ghostsoullesswhen you say stuck at a light, I assume you mean it pops after you start moving and then shifting, if so that and shift pops after riding for a long time are fine. If it's popping while you're standing at the light, you might wanna get that looked at.
@@coolgeevee Yes, after I start moving and shift into second and third usually. Figure it’s a buildup of fuel from idling for so long
@@Ghostsoulless it's not a buildup from idling because if it was; you'd hear a constant string of pops. Because once the buildup during idling reaches a point it starts popping in idle itself, that's why I asked if it happens while you're stopped.
What's happening with yours is the moment you shift you close the throttle a bit to rev match (maybe even unconsciously) there is one cycle where you sprayed a lot of fuel but because the throttle closed a bit you mixed a bit less air, so net effect you ended up with a rich mixture so the remaining unburnt fuel burned off in the exhaust.
You might have also noticed this doesn't happen on short rides but do on long, is just because temperature plays a role too. Overall, from your description, nothing major to worry about.
@@coolgeevee Interesting, I appreciate the explanation. Pretty new to the motorcycle world (come from classic cars), so always appreciate learning something new. Thanks again
Bro if you have time, please make a video on motorcycle security tips. It will be much appreciated
It's funny, because when I saw the headline, I just KNEW it was an opportunity for me to rip a new one into someone who, yet again, gets things wrong.
Alas, I temporarily forgot who I was watching.
What I really like most about your videos is that you get into the real detail of definitions, and you VERY APTLY explained the difference between a backfire and an afterfire.
It really is a hallmark of your Shop Manual Series of videos, and why I never hesitate to recommend them to friends. I know they'll get the best information.
Thank you!
I'm glad you appreciate the show Bill. Sorry to rob you of an opportunity to rip someone a new one, lol.
I don't mind a little bit of popping. Stock bikes do it, you just don't hear it much because the CAT and mufflers... well, they muffle the popping.
But once I do the exhaust and tune, I jam a marble in the AIR hose and 100% block that system. No need for block off plates, a marble does the trick every time...
I love you Ari, you're the reason why I work on my own bike, please don't ever stop making videos!
Decel pop on my 919 is my favourit thing about it 😊
😮💨🤤 so the slight popping sounds I get from my bike after installing an SC Project exhaust are okay, sound good too 🤓
What if the bike only afterfires without the db-killer, and is fine with the db-killer in?
lots of times your "decel pop" is caused by hot air from your engine mixing with cold air coming in from the surrounding air which makes a pop, it happens especially on chilly mornings/nights
My klx650 sounds like a 9 going off decelerating at high rpm but engines been professionally checked out lol
Great video. Nothing sounds better than hearing those backfires, ESPECIALLY under the bridge.
Guy watched the video and learned nothing 😂
As usual, I'm the 2-stroke guy just watching this to hear about what The Normals are worried about.
The most spectacular after-fires I've heard were both from bikes with bad ignition condensers. Super weak-ass spark leads to a TON of unburnt gas AND unused oxygen while trying to climb a hill or something. Eventually some of that weak sauce flame is still present when the exhaust port opens, and KABLAMO. A 2-stroke expansion chamber and stinger really makes this bigger and sharper than it would otherwise be. My cousin's 100cc Suzuki sounded somewhere between a .30-06 and a Civil War cannon. My 400 triple did the same thing in the street a few years ago, and it REALLY got peoples' attention.
Can it happen after opening an idle screw on carburettor too much ?
I have a suzuki sv650s with leovince slipon. When i have my db killer in i just get decel pops but when i remove the db killer i get gunshot like popping. Do the db killer do that much of a diffrence?
Great episode dudes
Can you do a shop manual video on safety wiring a bike for the track?
I currently own a Buell XB12 and the decel pops are out of this world, i love it. Rolling downhill i get the constant pops and bangs. Got a real backfire twice which sounds way different (having the intake right under your chin so you can literally hear the engine breath makes it easy to tell the difference). The combination of a 1200cc V2 while accelerating and decel pop while letting go makes riding so much more enjoyable.
(Remus exhaust + K&N air intake are a nice combination)
You like that? I tuned it out of my Ducati. I like an efficient engine, not a noisemaker.
@@CarsandCats efficient is quite difficult to achieve on this engine since there are very few people that know how to tune it and even less that want to do it. The nearest expert i got is located in a different country. As long as power delivery is linear and the engine runs healthy i am happy.
My 200cc made-in-India moto called TVS Apache is known for those pop sounds that are loved by many. However, they are only clearly pronounced when the muffler is hollowed, which I don't want to do on my bike. I wonder why the manufacturer doesn't engineer this into stock muffler as a feature bcs it's clearly loved by clients
Excellent information...
This guy is the BEST!
Nice vid man. You're right lots of modern bikes are designed for decel pop..
Good videos on this page. how come i do not see a hold at the tip of muffler to fit a db killer? i've seen some Yoshi with the hole some none. just the rubber plug on the carbon piece
I had a 21 xt250 that I put a slip-on on and that thing would shoot a foot flame when it got hot on hard trails. I figured it has no o2 sensor but is efi so when hot it is starting to run rich from hot air intake temps. Was defending cool but also kind of good cause I would know to go a little easy or maybe take a water break and let the bike cool down being air cooled and all
My 2002 Bandit had custom ground jets and was tuned by reputable garage. It also had a high lift intake cam and a slip on. Carburetors can’t be tuned like fuel injection and thus I had lean areas and rich areas. My rich area was roughly 6.5-9k rpm. If the exhaust was warmed up and I rolled off the throttle from at or above the rich area of the rpm band, I would get decel pops into decel bangs. There was nothing wrong with my bike or the tuning. Only because it was carbureted.
There's no reason carburetors can't be tuned for proper AFR. Folks been doin' it for decades. If your mechanic is suggesting that it's "because it's carbureted," then perhaps you should take the bike to someone that knows more about tuning carbs.
You forgot one major thing to check...Valve clearance. As the valve seats erode, the valve clearances become tighter, increasing valve overlap. Excessive valve overlap invites carry-over during the transition from the exhaust stroke and the intake stroke, allowing unburned fuel and air into the hot exhaust. By opening up the valve clearances, the carry-over is greatly reduced, reducing popping. Too much valve clearance will create more low end torque, but will reduce high speed torque. It also 'hammers' the valve train at higher RPM. When doing a compression check, tight clearances will show low compression, but if the compression seems 'too good', chances are, the valves are too loose.
My father had a backfire problem once on his bike, the cause was a camshaft sensor that was not working probably.
Hello and thanks for the vid. My bike is defiantly backfiring. It just started all of a sudden when I went to drive my bike home from a so called mechanic who I think messed with it. It was so loud and frequent. I could not even run. I had to have it towed. I would like to know the check off list of things to do to locate the problem.
Please and thank you.
My bike only decel pops when I release the clutch while slowing down.
Sounds great too
Had a TL1000R that would light up the night with a Yosh system installed. Awesome.
Finally, someone who knows what a real backfire is. 😁