Sportster backfiring.... why?

Yeah it has to be warm, the carb has to be warm or they fart/pop and back fire, nature of the diaphragm carb.

It does it, becouse of the factory dual fire ignition sysrem. Both sparkplug give ignition at the same time, so one of them gives spark when its not nevessary, and this spark ignites the air fuel mixture when the intake valve is open it can came back to the carb.
Single fire is better, altough i think its not worth trouble converting it, dual fire just works fine, most hd riders can live with some bacfire...
Put on the air cleaner cover.

My 04 does the same thing. Almost a hiccup at low rpms when u start to hit the throttle. I changed plugs, air filter, and ran some sea foam through a couple tanks of gas, but it hasn't changed yet. It does seem to get better once it's been ridden for a few minutes, but still occasionally happens. I thought the carb was gummed up, the only thing left that I can think of is the fuel filter...

Mine is doing the same thing!! What's the fix? Thanks!

I have 05. 883 it does same thing

Could possibly be one of these two things:

1.Bad crank position sensor (easy to replace)
2. Intake manifold seals need replacing

Finally I fixed the problem. it was the ignition pick up and the ECM. 

Just curious was the bike sitting up a long time previously to this happening?

Trop riche en essence .... Tu as trop d arrivée d essence ...

Yeah mine does the same thing if I don't let the engine warm up first. Especially on cold days. Once it's warm no problem. I assume it's normal just let it warm up for s couple of minutes before you ride it and you should be all set.

Can you please share more information? How did you fix this?

I have an '05 that did the exact same thing. I changed the intake gaskets and adjusted the idle back up to 950 rpm per the shop manual and it went away. Most sportsters do this and sometimes these parts fix it and sometimes they don't. I guess that's why the dealer doesn't want to fool with them.

I know this was 9 months ago but how did you figure out it was the ignition pickup and ECM? Is there a test for these? Mine has a similar issue.... had head gaskets replaced and crank position sensor.....

What would make your bike pop while riding down road

Its called the sportster hiccup . Almost all of them do it. Mine sometimes and I think its the dual fire ignition.

have you checked the vacuum or power to the VOES just behind the carb.

I think it might be the points

Is it Palestin flag ?!
BTW ... thanks for sharing the solution..

mine backfires when I ideal it down or cruise with low rpms. could it be the exhaust gaskets??

I have a 1974 1000 xlh at 65 or 70 mph it cuts out , why

Could also be, jetting, lack of back pressure or bad fuel and the other few things posted..FYI, every time you change the exhaust you need to check jetting and may have to re jet..

I had this problem untill yesterday. I toke out my carb and my intake manifold. Check if that is bent. Or has high spots (if you do sand it down cause air can seap thru) Check if the flanges are bent.(sand off all dirt and all pieces of old rubber) If they are bent get new ones. Place new seals (use bearing grease to make the job easier so they stick) handtighten the manifold (dont tighten) place the carb and airfilter. Now you can allign your manifold (if you dont you might misalign) take carb off again and tighten the manifold. Half a turn on each bolt. Else you comprimise the seal on one side. When its good and tight. Replace carb. And air cleaner. And enjoy your bike. Bit of work but easy to do by yourself. Just have to be patient. Prob have to take off fuel tank seat and horn assembly aswell. If you doubt you can put it back together just make pictures of what you do. Takes about 2 hours. Maybe 4 if its your first time.

Clean your carbs my brother

Ignition timing is all screwed up

Ny older one does that when running lean, inrich a little and it goes away.

Remove the plug that covers idle mixture screw. Turn counterclockwise 1/2 turn. Also noticed your cam chest is way to noisy but that's not causing pop out of carb

Es igual a la mía!!!

Its a older bike....time 4 a carb rebuild

My sportster is consuming fuel rapidly and backfiring into the carb, suggestions? And no it’s not leaking out the overflow

Change plugs
Make sure coil and ignition is working on both cylinders
Clean carb
Check gaskets

It's a Harley ! POP ! POP ! $$$ POP ! $$$ Again !

I have a 96 xl1200c. It was doing the same thing. I put new pugs and played with the gapping. Runs perfect gapped at 42.

1997 Sporster 1200C. Same thing. New plugs, CV Permorance fuel mixture screw, and rebuilt the carburetor. I had to tune the carb on the rich side because the intake has a slight leak. Runs fine for now.

I have the same issue with mine someone I bought it off of sayed cause it has a black gas tank and if u have it set for a while and don't drain the gas out of the tank and carb b4 u store it it does that was he right?

Bad intake seal

This Is a Lean Spit. Things to fix it. Check intake gaskets. If they are OK then look at you idle Jet. it is a stock 45 jet on a twin cam but sportster may be smaller. Buy some larger idle jets and keep upping the size till it goes away. Sea level should be 48 to 52 on a 88 twin cam.

try the crank shaft position sensor. it times the spark and fuel intake. cheap and easy to do yourself

You should prolly warm your bike up before you do dumb shit like this

Carb jets

Your intake seals are wearing out. The poping is air coming in from the weakest points on the worn seal. Oxygen is added to the mixture, on a deceleration of RPMs. More oxygen to the mixture makes it sensitive igniting itself where the leak is and burning everything through the manifold. In some cases smoke will burst.

OK I know this is an old video BUT I finally figured out the main problem with my 2006 harley 1200 custom... the spring that operates the accelerator pump was weak so it was not shooting enough gas when i would chop the throttle. I was watching it and it barely had enough tension to properly open that valve. I shimmed it with some tiny washers and my bike only pops like once or twice for like the first 10 seconds of idling i couldnt get it to pop once i was riding after a min of the engine warming up. If you have messed with jets and needle position and the air mix screw check that fucking spring dude!! Hope this helps!! It took me like a month to figure it out.

Sportster 2004... Idem...😢

Needs more air less gass

My bike is now making a click sound after a rough start where I didn't pull the clutch to start.

Timing cup sometimes gets cracked...inspect....

An air leak can cause this. I had to put a quality automotive hose clamp where the carb meets the intake manifold. I tighten it with a long 5/16" wrench from between the cylinders on the other side. It fixed my leak real well.

Intake manifold gasket possibly cracked or ripped

Every Harley I have ever owned carb or inj at some time or other will “spit” out the intake , I took my new at the time 2003 road king screamin eagle to the dealership and they said it happens to all of them, so I put almost 80k miles on it with no problems