mine as pick up a low throttle stumble or miss as some would say. clean carb to no pevail. unplug my air mixing screw and check and it is turn out one full turn from close. seam like I read it should be 2 turns out. went out 2 turn and it seam to be rich and my enricher didn't seam to work right. hard to choke it . carb is stock with the #45 slow jet, and I belive the #175 main. any sugestion to removing this miss. it is missing right when I am rolling back into the throttle. give more throttle and it is fine. thanks. 1990 flt stock evo engine.

 

Could be the accelerator pump, but more likely a slight vacuum leak. That can come from a manifold o-ring, carb grommet, VOES vacuum line, diaphram or the enricher valve not seating.

If you use the "spray it with WD40, carb cleaner, propane" method and listen for a change in sound, get someone to hold a tube of some sort at the carb intake because any vapor it pulls in thru the throat will give a false indication of the leak, especially when checking the mainfold/carb grommet.

 

Move the slow jet to a #48 The 45 might be starting to varnish closed

 

wouldn't it make more sense to replace or clean the 45?

 

Though alot about rebuilding my CV, was having some of the same problems. I put a Mikuni on it and really like the carb. Dialing it in has taken some time but think I am about there.

 

Stock except for pipes and air cleaner? The old standard is 2-2 1/2 turns out idle mix
screw and replace the needle with 1988 Sportster - needle N65C part # 277094-88.
Clean carb with Gumout Jet Spray while it's apart.

If you have a vacuum leak, it will not fix / cover it up - just put your jetting spot on.
IMHO.

 

some things that I have already done. new intake and carb gasket. new voes vacum hose. spray wd 40 over every thing looking for a vacum leak. I change the #45 jet with a new #45 jet. pull needle out and clean it and check the diapram for a tear. none found. one question I have is this, how can you tell if your enricher has a vacum leak? other than that I can't find a vacum leak anywhere.

 

one other thing. stock breather but I have samson slip-on muffler. I have had muffler on for a while with no problems untill recent.

 

The enricher leaking is very rare and I probably should not have even mentioned that, at this point.

Now this is gonna sound dumb, but I had similar symptoms once and turned out to be a crappy spark plug. They were "V-fire" plugs and with low miles. Try some new Champion RN12YC plugs (they're cheap) and lets eliminate that possibility

 

Would the plugs cause the bike to stumble only at low rpms? I am having a similar problem with my 93 flstf. I have cleaned the carb, checked the diaphragm, put my old stock ignition module in, put the stock coil back in, (I had changed them to Screamin Eagle several years back, and after some digging found the old ones). Pulled the plug wires off my shovel and put them on, changed the gas, and checked the seals. Damn thing still stumbles violently under load at heavy throttle and low (1000-1500) rpm. Once it's above about 2500 rpm, it takes off like a rocket. Well, as well as a slightly modified 80" evo can resemble a rocket anyway.

Update - Problem Solved!
Finished putting things back together last night at about 10pm. I bought new intake and carb seals, and brand new plugs. Took it out for a test spin, and nothing had changed. However, this was the first time since the problem began that I had ridden the bike at night. When the bike was missing/chugging, I noticed a barely perceptible flicker in the headlight. Today, found that the cable at the starter was either broken loose or about to break. Not sure exactly because it came free real easy when I gave it a wiggle. Replaced that, and it pulls fine all the way from 1000 rpm up. I'm just amazed that the bike was able to start with the cable in that shape.

Oh yeah, I figured out by reading some other posts that by posting my problem within this thread that I was "poaching". Sorry, and won't happen again.