04 Sportster 883 Carb Issues

I took the bike out today to try and see if the bike was not going pop with the mixture screw adjusted where i thought it needed to be(3 turns out). Once i got it out on the road it popped twice within the first mile, i thought that may because it wasn't fully warm yet, so i ignored it. But it continued to pop, only when i was approaching i stop sign or a light and i would hold in the clutch while coasting and then crack the throttle. Also did it once or twice when i would crack the throttle just before beginning to release the clutch and take off. So in my previous post when i said that it was stopping when it was 3 turns out, i was wrong, just not as common. It doesn't seem like anything that i am doing is changing the situation, really frustrating.

Did you check the accelerator pump diaphragm for signs of pin holes or cracks??? Do you get a good squirt of gas from the accelerator pump nozzle when you crack the throttle??

the accelerator pump diaphragm looked good, but i bought a rebuild kit a few weeks ago and i went ahead and replaced it today. then rode a round the block a few times, still popping. when i crack the throttle the squirt of gas looks good, but im really not sure what it should look like.

Ok, i took the carb back apart, cleaned out the pilot jet passage and the mixture screw passage and went for a ride this afternoon... it seems like that if i adjust the mixture screw the way that it is described by cv performance(start at 1/4 from the engine stumbling) then the engine hesitates when i crack the throttle, i have to take it out to about 3 turns (when i started at 2) to get it to rev smoothly, but even at this mixture i have a pop occasionally from idle. My grandpa used to work on cars and he said that sometimes those old cars would pop when they we slightly out of time, i have not messed with anything to do with timing on the bike and i know the previous owner didn't either, but could it get out of time on its own? and would that cause these symptoms? Any new suggestions would help...Thanks

Geeze, jeffrey you're having a hell of a time with it...did you rule out intake leaks...at the carb mount and at the head/manifold gaskets??...I really can't see how it would get out of time by itself....

I have replaced both of the gaskets at the head/manifold, and I replaced the boot that the carb fits into also, all just to rule those, the original ones looked fine.

I checked the direction of the needle jet nozzle and it was correct... an unrelated question(maybe), what is the item the is circled on pic 1 and in pic 2, i have looked through my repair manual and i can't find it. It was screwed in completely tight, is that the was it should be? Sorry if these are dumb questions.

That's a float bowl drain screw...funny thing is,I didn't think CV's on a '04 had drain screws or an over flow tube on the float bowl anymore...

To better explain when the popping occurs:it happens any time i quickly crack the throttle and let it go back to closed, never pops while under load, only from idle. As a habit i generally crack the throttle once prior to beginning to release the clutch and take off(probably a bad habit), this is where it has occurred most often, second most common time is when i am coasting to a stop light and the clutch is pulled in and i crack the throttle quickly... a friend of mine has the exact same year/model sportster and his does not have any popping issues. I personally suspected that it had something to do with the accelerator pump, because i have read that it is what provides fuel in instances where it is needed quickly. The diaphragm, spring and all o-rings have been checked and replaced, just in case, with no correction of the problem. on another post i read it said that the float had something to do with the accelerator pump operating successfully, could that be the problem?

In mine it is all coming from the carb, I have had the pop pop pop on develop a few times when I have been experimenting with rich mixtures trying to get rid of mine main problem, but the issue i have only occurs when I open the throttle quickly, as if it is not getting enough fuel fast enough or it's getting an extra shot of air from somewhere it's not supposed to, ie leak.

How about trying not to blip the throttle whenever you are about to pull in the clutch? See if it is that doing it? I guess you haven't really said either, how aggressive or at what speed (What MPH) are you experiencing this. Are you rolling hard on the throttle, like you are pounding through the gears, or are you granny riding?

I usually crack the throttle just before releasing the clutch from a stand still, only time it does it while I am in motion is when I'm drifting with the clutch already pulled in. It only happens when I crack the throttle quickly so if I don't do that then it won't pop, ever, if that's the solution then I can live with that, but my buddy's sportster I can crack the throttle from idle as hard and as fast as I want but it will not pop.

Are both your bikes set up the same? What are you running for breather and pipes?

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have you eliminate that your pipes aren't loose at the head? Clamps, that you didn't pinch the rubber diaphragm at the carb cover. Just in the intrest of thoroughness, check leaks around the intake at the carb, intake at the heads, head gaskets, etc. Just another dumb question, but I am assuming that your bike is up to temp when this is going on? You didn't say how fast you are going when the popping happens? Is it at any speed or not?

Hey, Jeff.
I don’t know where your idle RPM is currently set to, but you may want to try slowing it down just a little bit and see if that helps. I know my 88 is sensitive to idle speed and popping back through the carb. I ride similar to you, little blips before letting the clutch out just to make sure it’s going to be there for me. I think it may be from years of riding 2 stroke dirt bikes, it just feels right… GOOD LUCK..

well all carb circuits and intake and seal boots have been covered and as far as timing goes sportys have a real problem with the pick up coil behind the points cover they melt ! second is the map sensor port gets restricted from fuel varnish and the map sensor is what advances the timing when vacum is lost on quick throttle snap . thats were i would look sounds like your slightly retarded on initial quick snap as rpm quickly comes up your timing is lazy . it will cough out the intake and if you continue to do so you will blow the side diaphram bellows. good luck.