Hey everyone,

I just got my first Harley (2003 Harley Sportster Custom 883) and I am having some issues with it. The bike was garage kept, but never started, for 3 years. I went through the basics:

Removed, cleaned, and flushed gas tank
replaced fuel line and fuel filter (installed inline filter)
cleaned carb thoroughly and replaced gaskets (jets cleaned)
replaced battery
changed oil
replaced grips

Other than that the bike is stock as far as I can tell. I got the bike to run and she sounds good at full choke, and will run decreasingly well as you release the choke. I adjusted the idle screw and was able to barely keep her idling without choke after she warmed up. However regardless of choke as soon as I touch the throttle she tries to die. If I keep it throttled she dies quickly. I have pulled the carb off twice now, I checked all ports and soaked in carb cleaner. I also replaced the carb/manifold gasket. I put a gallon of premium and some Lucas and Seafoam in the gas tank. Could it be possible I have too much treatment in the gas? Would that cause such an instant response from using the throttle? I have been working on this for a couple of weeks now so any help would be tremendously appreciated. Thank you all in advance!

 

How does the slide diaphragm look? Is there any holes/ well seated under the cap? Is the cap tight? Does the slide move freely or does it bind up? Is there spring pressure to keep it down or did someone mangle the spring? That is where I would start, the enrichener circuit does not rely on the slide and the idle circuit runs behind the slide but the throttle response is controlled by the slide. Also check your accelerator pump operation, when you twist the throttle a jet of fuel should shoot into the throat of the carb to reduce flat spots in the throttle when accelerating. But the top end of the carb is where I would start at this point, maybe there is a tear in the diaphragm preventing the slide from rising when the vacuum pressure increases behind the slide. If the top end checks out, check the float adjustment, maybe the float level is set too low causing a lean condition upon acceleration, or if it is set too high you would get a bogging down and stumble on acceleration.

 

Check that the needle jet is installed correctly, it can be installed upside down and will cause the symptoms you describe.

The needle jet is the part that protrudes into the carb throat from the bottom (the lower part of the jet slides in it).

 

also make sure you put the needle jet in before the spring and spring seat...that may also cause the same symptoms...

 

I just got a '01 Sportster 1200 with similar issue. Starts good with enricher, even at -10 C but takes a long time to warm up. Pops back out the intake and hard to rev up. If pampered it, it will pull well at 1/4 to WOT. Seems lean so I took carb off and found idle jet plugged. Cleaned that and put carb back togeteher. Haven't tried it yet because I noticed that after opening the throttle, the AP push rod does not return quickly. Gives a good squirt the first try but doesn't refill. The rod stays about 3/8" below the cam actuator. I stretched the spring but no change. Is there a stronger spring available? Is this a common problem?I have a HSR42 Mikuni flat slide carb. Sorry to hijack your post.