Little help here, please.

I've never played with one of these Harley carbs but I've worked on carbs before.

Bike is a custom softail 96" S&S. Super E carb shorty. Big sucker intake. All stock internals. It had LAF pipes on it and of course they where mega loud. Ran fine, I guess. Too distracting for me. I bought a set of Rush mid length pipes. Baffles and 1 3/4" pipes. Put them on and bike runs great. Much better low end. Pulls better sounds better etc etc. Not real happy with the sound when backing off the throttle. It's a whispy windy noise.


Cold idle takes about 30 seconds of assisting the throttle to idle without stalling. Warmed up, idles forever.

So I pulled the baffles....Oh yeah!! That's it. Louder but sounds much better. I'm ok with it. Idles good warmed up and pulls strong. God this EVO vibrates.

The problem is, at steady state low rpm/barely any throttle, cruising it seems lean to me. It surges a bit. Not too bad but would be nice to try and correct it.

I know where all the adjustments are on the carb....little more accl pump or maybe a bit more fuel mixture??

I dunno, so I ask.

Thx for any help....

 

If the issue happens at a steady cruise, low RPM, it sounds like the "slow" jet (also called "intermediate" jet) needs attention. If it's lean enough it will "cough" through the carb, as the spark chases the fuel up the intake, trying to find more fuel. If too rich, it can "stumble" or "blubber". S&S instructions say that the leanest jet that alleviates this condition is correct. So when tuning the slow jet circuit (which you do after you've propoerly adjusted the idle mixture) replace the slow jet with the next leaner jet and ride it til it's at operating temp. Repeat until it starts to cough through the intake, then go back up one jet size. This should be correct. Now readjust idle mixture.

Idle mixture is adjusted by slowly turning idle mixture screw in (clockwise) until the bike runs rough. Now back it out slowly just enough to make it run smoothly. Idle speed should be around 1,000 RPM, which gets set via the idle speed screw (as opposed to the idle mixture screw).

 

Drag pipes on an Evo........
Install an 1 1/2" long 1/4" bolt in the pipe using the hole that held the baffle, and stack 4, 5/16" nuts on it, and then nut it with a 1/4" nut.
It'll have all the racket you have now, but it'll control the reversion that occurs with open pipes.
Now, moving to the carb.......
Base line jetting for set-ups like that, from what we've found is as follows;
.0295 pilot, 1 1/2 turns out air/idle screw, bottom the accelerator pump screw and back it out 3 turns, and a .070 main jet.
This should get you into a civilized fuel curve, and then you can makes moves as needed from there.
Scott

 

I might very well of turned the acel pump screw last night.

if it's surging/jerking then which way should I go in or out on the screw?

The bike didn't do this with the LAFs or the baffles in. I might have created this.

I will do the bolt and washers. I read that gives it a little back pressure to help along.

Thx for the help by the way.

 

I did the bolt/nuts in the baffles hole. That was a little fun getting down in there.

Still not sure on what to do with the accel pump...turn it in or out?

 

Screw it all the way in, then back it out, 3 complete turns for the baseline setting.
Scott

 

I put those bolts/nuts in the pipes and most of the surging went away. It's definitely tolerable now.

 

Now jet the carb, and it should get better yet.
Scott

 

change what jet to what?

 

Check post #3 in this thread (the same post where the bolts and nuts were recommended). Jetting recommendations were also given in that post.