Frustrating Carb Coughs & Octane?

Discussion in 'Softail Models' started by BigAl66, Jun 10, 2011.

  1. Slo-Ryd

    Slo-Ryd Junior Member Contributor

    I've been battling a carb cough 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 especialy when blipping the throttle while down shifting as I came up to stops. :wall

    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 (except when I knew there was an intake leak and the idle was all over the place from light to light) and the plugs although a little tanner/darker than I would like indicate that it's a bit on the rich side.

    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 87 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.

    Great forum btw:s

    BUBBIE Well-Known Member

    I would stick with the 93. The problem after it is sealed properly at the manifold COULD bee the excel-pump not giving the Proper amount of Squirt when twisting on the throttle....

    I went to a mikuni 42 just for this reason; better adjustment at that location for the Best running with that problem...

    If your problem, take a look with the air filter off and twist throttle to see If you get an Early FULL squirt....

    If this is not working properly here NO amount of slow jet change will stop the hic-up.

  3. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    As bubbie has stated the mikuni hsr 42 is a good way to eliminate this sort of problem as when you open the throttle with the cv this opens a butterfly that allows more air to be drawn into the cylinders that draw of air will produce a vacuum and lift the carb slide
    the time lag between the butterfly opening and the slide being drawn up and the needle with it may be the cause of the wee hic at times
    the mikuni has the slide directly operated by the throttle cable

  4. 2000classic

    2000classic Active Member

    Do you know at what rpm the bike is idleing at? I ask because I had a 91 Ultra that behaved the same way until I brought the idle up to the recommened 1000 rpm. Problem was gone!
  5. Jack Klarich

    Jack Klarich Guest

  6. Slo-Ryd

    Slo-Ryd Junior Member Contributor

    Thanks for the input guys and the link me I know and understand the workings of the cv thouroughly:s

    As for the Mikuni.....although I've heard great things about it, I'm happy with the CV's performance and I know the Mik can be a little finicky to dial in initially. I'm just not ready to throw that kind of $$$ at it for such a minor nuisance. Besides, I bought this bike with an S&S Super E on it and abondoned it in favor of the CV. I've run them in the past with no problems but this one was well worn especially in the shaft bushing area so I ditched it vs. trying to have it repaired.

    Fuel squirt seems adequate, although occasionally I notice some lag if I sit there continually blipping the throttle with the AC off. I think it's just the delay in the recovery of the diaghram priming with a fresh load of fuel for the next squirt. I have a rebuild kit coming and that's my next step, primarily to replace the diaphram. Diaghrams alone were $8.50 alone vs. $11.99 for the whole kit so the choice was obvious.

    Now, if someone would just come up with an aftermarket adjustable Acc pump assembly for our beloved CV's it would make a great carb even better. I know Motor Factory and others sell an upgrade kit to the check ball and spring assembly so that may be an option down the road if it improves the squirt.

    My problem with products like these are they are permanent mods that can't be reversed and still leave you with no adjustability.

    I'll keep you guys posted if I ever get it sorted and appreciate the replies so far.

    I set it at 950 with a tach I use for tuning and agree, If I set it too low for an aggressive lope, it seems worse:s
    Last edited by a moderator: Jun 11, 2011