Hey everyone, bear with me so I can explain from start to finish. To speed things up, skip to the last paragraph for my current issue.

Beginning of June I rode my 2006 Sportster XL883C from Billings, MT to Pocatello, ID (long ride for this bike). I noticed, not for the first time, that at high speeds (80+ mph), the bike occasionally fights me and pulls back on the smallest of inclines, but not consistently. When I got home, I decided that I would replace the air filter and clean the carburetor as both were badly in need. Air filter was easy and after finally removing the stripped screws holding the carb float tank on, I was able to get to the jets. After cleaning everything I went to reassemble and ended up snapping the needle jet holder at the threads. When I replaced it, I managed to forget to put the main jet back in place, causing the bike to run extremely rich and refuse to go faster at the higher end of the gears.

Fast forward two weeks and I finally have a chance to replace the main jet. I get everything reassembled and find that I am idling extremely low, at the point of killing the bike. Most of this was fixed by tightening the idle throttle screw on the side of the carb. I also decided this would be a good time to do a full tune and drill out the plug covering the mixture screw. I get it adjusted and end up setting the mixture screw about 2 turns out. The bike now runs like a dream. The next morning when I go to start the bike to go to work, I have to turn it on and let it sit for a minute, because even with the choke on, it is killing itself if I touch the throttle. The bike warms up and this issue goes away. I get on the interstate and find that I am maxing out my throttle at 80 mph in 5th gear. At lunch a couple of us go out to look at it and end up readjusting the mixture screw, assuming that I am running rich. We turn the bike on and let it idle as I adjust the mixture screw. I slowly turn it in (clockwise) until the bike starts to stutter, and then I back out 1/4 to 1/2 half of a turn, leaning it out. Go to drive home and now the throttle is maxing out at 70 mph. I can hit that 70 mph in 4th gear, and then when I kick it to 5th, I can feel the bike shift but I don't get any extra power or speed.

Thoughts? Going to tinker with the mixture screw a little more and also make sure that the main jet I put in is the same size I had in originally (175) but I feel like I am missing something else.

 

what are your jet sizes, pilot and main? what pipes and airbox setup are on the bike? any other mods? are the brakes dragging?
m

 

Check you cable adjustment and throttle stop screw adjustment. There is a stop on the throttle at the carb. If it is hitting the stop too early this will explain your problem.

I agree, more info please. What carb, and what jet sizes, more info needed as mentioned above. Do you have a factory repair manual for it? YD

 

So you broke the emulsion tube and had to replace it? This is the tube the main jet screws into. If so did you replace the needle tube (silver goes on top of the emulsion tube and can be seen by looking into the carb) and is it on right side up or upside down? Is it installed at all?

Yankee dog is correct in making sure that wide open throttle (WOT) occurs at the carb and not at the throttle end. The butterfly valve must hit the stop(lightly) on the carb body, and not just run out of cable pull. Adjust the throttle push and pull cables before doing anything else. You may find that you will have to adjust that idle screw on the side of the carb again.

 

post the jet size changes. a large main will cause decreased speed as the rich mix will not burn.
do not over look the slide diaphragm.

 

This.

Needle jet installed upside down

 

Quit screwing with the idle mixture screw, that don't do **** on the highway. Hence the reason it's called the IDLE MIXTURE screw.

Yea, what's your jet sizes? And how much of the carb did you take apart? I'm guessing you assembled it wrong. And FYI, a 175 main is too large for an 883.

 

Thanks for the response. “Most” were helpful. I’m here to learn so thanks to those of you that took the time to respond without acting like I’m an idiot. The bike is now running like a dream.

To answer the questions that people were asking:

The needle jet was in place correctly.

All systems on the bike are stock as far as I am aware though there was an owner before me. All work I have done on the bike has been with OEM stock parts.

The jets are what were in the bike when I bought it, 180/48. I have now replaced the pilot jet with a 45.

I bought a rebuild kit and replaced everything from seals/boots to jets and a EZ adjust idle mixture screw.

For the one that said that the idle screw had nothing to do with it, that was the only adjustment made between the throttle maxing out at 80mph vs 70mph so despite the lack of supposed correlation, it had an effect.

The bike now rumbles beautifully after the rebuild and a good carb tube. Hitting over 100 mph easy on the way to work now.