04 Sportster 883 Carb Issues

I bought an 04 sportster 883 off of a friend... only 5000 miles and i was told that it ran fine... I have found one problem that i cant seem to correct. When the bike is at idle and i crack the throttle it will occasionally pop/backfire through the carb. I have attempted some adjustment and cleaning with no luck. My friend says that this never happened before. The bike basically sat for approximately one year before i bought it. Any suggestions would help...Thanks

i have dismantled the carb and cleaned it thoroughly, the plug was removed before i bought the bike and i have adjusted the mixture screw everywhere from 1 to 3 1/2 turns out, prior to taking it apart this time. To further explain, it only does the popping from idle, not under load. I am going to replace the manifold gaskets. Any other ideas while i have it apart, ie starting points for making adjustments? I also have an adjustable needle in there that im not familiar with, right now it is adjusted to the middle notch with 3 washer under that. Any advise on that would help. thanks

By the sound of that you have a dyno jet kit in it....check the vacuum port in the slide...a 7/64ths drill bit should fit tight...if a 1/8" bit fits in the port, there's your problem...the slide was drilled and jumps open too quickly giving you the popping when you crack the throttle...if that's the case you'll need a new slide and then I'd toss the jet kit and get stock parts(slide,jets and emulsion tube..or a CV stage 1 kit and a new slide)

See if this is what's in your bike...Dyno Jet kit instructions..click on the pdf file....

http://www.dynojet.com/jetkits/motorcycle/harley.aspx

Ok, i checked the slide and a 1/8" drill bit easily fits in the hole, the next size up does not though. That is definitely the same needle as is in the dyno kit. i will get a new slide andi have a stock needle, and see if that takes care of the issue. thanks for the advise. i will post what the results are.

Forgot to mention earlier, you'll probably want a new spring too...dyno jet kit has a shorter lighter spring...sometimes using a stock spring you can get away with the drilled slide...stock CV parts and dyno jet parts aren't interchangeable...check with your buddy to see if he still has the stock parts...spring emulsion tube and jets...

If you are still having some issues and need parts, I have a spare Sportster needle that I can part with. Hope you get it worked out.

Thanks guys... I am waiting on the new slide now, should be here the first of the week. I'll let you know what happens, a have all the parts of a stage 1 kit so i am going to put those in when the slide comes. Thanks again

Good luck...keep us posted

Ok, I put in the new slide and went for a ride... No coughing, popping, farting, backfiring, or whatever you want to call it... Seems to be fixed, I did notice a slight hesitation when trying to accelerate from around 40 mph, I assume I may need to go up a size in the main jet? But my problems seem to be gone, thanks for the help guys, any suggestions on the hesitation?

Check your accel pump. Sportsters are notorious for having that dead spot. Check that diaphragm and make sure that it is good first. Glad to hear that it is much better.

Maybe I jumped the gun a bit when said that it was fixed... I took the bike out today, and it did the coughing several times... It is pretty cold today, about 50 degrees when I started, so I thought that might have something to do with it? Also when I replaced the slide I took out the jets that were in it with that Dyno kit, they were 45/180, and I put in the jets that came with my stage 1 kit, they are 44/175. Could that be it? Or just the cold? I'm confused.

Was the bike up to running temps when it was coughing or was it just in the first 10 minutes or so?? 44/175 should be good for jets...did you set the idle mixture too??

Harley Davidson Carburetor Performance Tuning

Yes, it was up to running temp, I had bend riding for several miles...not sure if this is worth mentioning or not, but the other day when I rode and it didn't cough I didn't have the air cleaner cover on, just had the air cleaner on. I put it on today before I rode, could that possibly have anything to do with it? I'm going to start from the beginning of the cv performance tuning procedures and go from there.

You wouldn't think the cover would have anything to do with it...popping through the carb is a sign of being lean...
Starting from square one is a good idea...

Ok, I just went through the process of properly adjusting the carb... I got the adjustment to where there was no evidence of lean or rich on the plugs.. However at that mixture I have the popping. When I make the mixture too rich, by about 3/4 to 1 turn the popping goes away. But I get black plugs and probably the things that go with that ie poor gas mileage... Any ideas?

Can you post a couple of pics of the plugs?? Set it to where the popping is gone and run a couple of tanks to find out your gas mileage....