883 Carb Farts

I recently purchased an 2004 883 for my wife. The bike only has 1300 miles on it and it had been sitting for a while. The bike back fires through the carb just off of idle, but it runs great throughout the rest of the throttle range. I removed the carb to clean it and to my surprise it was very clean. I also changed the plugs and wires, changed the oil and the trans fluid. After doing all of this I still had problems with bike backfiring through the carb off of idle. I then drilled out cover over the idle richening screw and found it adjusted two turns out. I tried adjusting it from 1 1/2 turns out to 4 turns out and it did not solve the problems of the carb backfiring. The stock pilot jet is a #42 and I tried replacing it with another # 42 thinking maybe the one was dirty with how small of a hole there is in the jet. I also tried a #44 and #45 jet and the #44 did not make a difference and the # 45 made the bike to rich through low to mid and did not take away the carb farts either. I am at my wits end with this bike. If any one has some insight for me I would greatly appreciate it. I do not know where to go from here except to the dealer and pay an arm and a leg.

Thanks,
Jason

What is the best way to check for manifold leaks. I did spray carb and choke cleaner around the manifold to see if it changed the idle while the bike was running and it did not. Is there another way to check for them.

Yes, the accelarator seems to be working properly from what I can see. I sprays as soon as the throttle is cracked open and it is spraying towards the middle of the carb throat.

Hello Jason,

I had a similar problem with my 96' Sporty 883. When I would roll on the throttle I would have a terrible stumble right away. Once the rpms got up there then it would be ok. I tore the top end apart due to redoing my whole bike. I decided to put a 1200 kit in with different pipes and a heavy breather. I went one step up on both the primary and idle jets and had a carb kit put in because it was discovered that my accelerator pump was sticking. Did you change both jets? Timing could be off as well.

The air cleaner and pipes are both stock. I did try changing the slow jet, but it did not help and I put it back to the stock # 42 jet. Would timing being off cause to back fire through the carb only right off of idle and run fine throughout the rest of the range? Some one told me today that it could possibly be the crank sensor out of adjustment?

had bought an 883 06 model, had beesetting for about 6mos, dropped a quart of seafoam in the tank, ran it like i stole it and now runns great........oh ya same symptoms

I guess with a motorcycle I am not exactly sure how they are timed, but I am assuming that one can advance or retard the timing. If your timing is off just enough, yes it can backfire through the carb. Then as your rpm's increase, then your timing advances enough to where it runs normal. An example of this is drag racers do this to increase low end power.

With it being an 04 there isn't much you can do about timing with out going to an after market ignition.
I think Kens carb kit will do the most for it.

Prior to 2004, Sportster "carb farts" were nearly always due to the needle that came in the carb from the factory & the most common replacement was the infamous N65C. You can see the problem when a stock bike is run on a dyno with an air/fuel ratio "sniffer" - in the 2500 rpm range, the mixture spikes way lean for a moment - up into the 16:1 - 17:1 range. Increasing the slow jet size turns the spike into a bump & while the "seat of the pants dyno" may say the problem's gone, it's not - you just drowned it.

But from what I've seen, the needle that comes in the '04 - '06 Sportsters works just fine, so the next thing I'd look @ would be the diaphragm in the top of the carb. If it's gotten brittle, is cracked, torn, has even a tiny hole in it, etc., the slide won't work right & since the needle goes up / down with the slide, the needle won't meter fuel right either. The diaphragm has been known to tear when the engine is started back up after the bike's been sitting for a long time.