Carb cough, CV, just off idle

Discussion in 'Dyna Models' started by Freewheelin Franklin, Mar 9, 2011.

  1. I read endlessly about CV carb coughs. Here's what worked for me, on the cheap (which is my religion).
    After buying a 2000 Dyna Wide Glide a year ago for half price from an unemployed friend who was moving in a hurry, I started to work on the low speed (and dangerous) carb cough. You know, one of those that gets you while low-speed turning.
    It idled pretty good, and ran cheetah strong, with some backfiring. My friend had bought it from original owner who had added a cam, intake, Vance & Hines.
    My friend had a skilled private mechanic work on it. While he could get most of the cough out for a while, it was still there, and would get worse whenever it sat.
    The air/fuel mix screw access was already drilled out. I adjusted it up and down numerous times. Slight help when I richened it a turn. Dealer said carb is beat, wanted to sell me an aftermarket carb, $450. No way.
    Read about the drilling, washers, etc.
    But here's what worked for me, completely curing the cough and backfiring.
    1. Drive that thing. CV hates being ignored.
    2. Lucas gas treatment, half small bottle every other tankful. About $5 per bottle.
    3. BP regular, and nothing else.
    4. Take off carb, put on glasses and clean it like you love it.
    5. Go up one on the main jet. In my case, it was going up to a #50, which is apparently the end of the line. (The number is stamped on the jet.) Cost, $4.25, Departure Bike Works, Richmond, VA.
    6. Adjust air/gas mix screw back to stock-plus. (All in, then out two turns.)
    7. Over the next several rides, adjust that screw until it's right. Smell it.
    8. Keep riding that thing.

    I've had the pleasure of riding many bikes. This is the sweetest-running, best-starting (even at 10 degrees F), strongest-running lightly modified Harley I've ever twisted.
    Best of all, $4.50 versus $450.

    Attached Files:

    Last edited: Mar 9, 2011
  2. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

    A .050 jet is A LOT of fuel for most bikes. I would be interested in what kind of mileage you are getting.

  3. eleft36

    eleft36 Junior Member


    I have had the same off idle problem on my sportster.

    The last time i tinkered with it I tightened the "choke" enrichment cable and snapped the plastic flange, duh.

    When I removed the enrichment cable and valve I was surprised by the amount of carbon on it and in the hole.

    The valve plunger has a composition seat which was loaded with crud, no way that could seat.

    After cleaning it and replacing the cable the bike idled very lean and ruff.
    I needed to turn the needle out almost a full turn, it idled smooth and steady and accelerated very smoothly without any pop back.

    I believe the enrichment valve was not seating and was giving a false idle mixture and preventing the pilot jet to function properly do to the compensating lean setting at the idle needle.

    You should check the spark plug color to verify the fuel mixture.

    Like Bodeen, I think #50 sounds rich.


  4. MPGs, between 35 and 45, depending on my mood. Surprisingly good, considering the jet.
    Plugs perfect. Pipes right.
    Like I said, it's got a cam in it, not sure which one because I didn't put it in. But it's got plenty of guts and one heckuva lope. My biker buddies who have way more expensive and more modified rides love my stripped-down 88. Original owner may have done some head or piston work. Don't know, but probably not.
    Checked the enricher early on, along with carb seating. Even replugged the air/gas mix screw access hole (chewing gum) because the dealer told me that it could be sucking a little wind through there.
    But it didn't come together until I changed the jet. Difference is amazing.
    I know it sounds funky, but that's why I posted.
    It was the final cure for me.
    The other steps - daily driving, good gas, Lucas treatment and the carb cleaning got most of it out.
    You know you've got it dialed in when it's freezing and you can pull out the enricher and pretty much just bump the starter.
    I've got friends and acquaintances with CV Harleys who have some version of the cough. Many of them are fair-weather riders.
    My view, the CV is simple and faithful, but very, very jealous.
  5. eleft36

    eleft36 Junior Member

    Good going.
    I can tune my softail with out getting gas on my hands, it took a little getting adjusted to.
    I love it.

    I think one more rain storm will have the mess melted away and I'll be out there.




    NEWHD74FAN Experienced Member Retired Moderators

    I also am a believer in CV carbs being pretty well sorted having been in production for over 15 years. Following the recommendations on the HDTimeline website is spot on...certainly worked for me. As for the odd jetting, having the drilled emulsion tubes, could very well demand a radical change in there...did you change the needle or see a number or mark on it indicating if it was stock or part of the aftermarket stage I kit or previous owner's kit?
  7. jaxdwg

    jaxdwg Active Member

    I believe you've overcompensated with the idle jet. I went to the 48 idle jet and raised the needle 1 washer and am running a 195 main with 95" and cams and exhaust. Getting 40 mpg and have the idle mixture turned out 3 turns. It runs good and NO coughs at any rpm and no rich smell at the pipe at idle. The further out you turn out the idle mixture the leaner it gets. I asked on the forums here to be sure I was right that the further you open the jet the leaner it gets. It sounds to me like you are compensating for the lean mid-range by using a really fat idle mixture. Just my 2 cents
  8. Slo-Ryd

    Slo-Ryd Junior Member Contributor

    Glad you got it sorted out and not to thread-jack but, I've been battling a similar problem since last year. 1990 80" Evo with an EV27 and V&H Short Shots with baffles. I tried the James blue intake seals, which I was told would guarantee to stop intake leaks......well I sprayed some WD on the intake flanges from the horn side this past weekend and lo and behold, the Idle stumbled. Trip to my toolbox and out came 2 new HD stock intake seals and on they went. I took my time and made sure everything was lined up and used some dish detergent to slippery them up. Put everything back together, dropped down to a .45 from .48 pilot and took it for a ride to test and get it up to temp. Cough was still present, and actually seemed worse. Came back, resprayed WD and found no change in idle so I stand here thinking the intake seals are not/no longer leaking. Put the .48 back in, re-rode to test and it's back to the occasional cough. Does it only after idling at a light for a minute or so and blipping the throttle to take off. Runs and pulls strong everywhere else, even idles well and the plugs although a little tanner/darker than I would like indicate that it's a bit on the rich side. Now, the OP mentions regular gas only.......this is something I'm wondering if he's hit on. From what I've heard, 87 octane fuel actually burns hotter and is easier to ignite than 93 which is all I've ever run since I bought the bike 2 years ago.

    Could this slightly richer pilot, and 93 harder to ignite fuel (if true) be the source of my frustration? I plan on running this tank out and give the 83 a whirl. I only ran 93 to eliminate the possibilty of detonation (never heard any pinging) My timing is dead on at 32* which early Evos are very picky about, and I don't tend to lug it around in higher gears up hill or when riding with the Mrs.

    Any suggestions or thoughts would be appreciated.
  9. JesseM

    JesseM New Member

    I just bought a Mikuni flat slide "easy kit" for mine and it fixed all my CV problems. Starts easy and runs smooth as silk.
  10. glazier

    glazier Junior Member

    I'm pretty sure that the further out you go with the mixture screw, the richer the mixture gets. Glider can verify for us, but I'm 95% sure.
    (it's the other 5% I'm worried about)