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Help me tune this CV carb please

Discussion in 'Motorcycle Tech Talk' started by snydley, Jul 14, 2011.

  1. snydley

    snydley Active Member

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    Hey Guys,
    I've got the CV carb installed and running well on my 1988 FLHTC and I thought I was done with it, BUT, I put new plugs in it and ran it around for the past 2 days, checked them tonight and they are ash white, with just a very little brown on the front plug. Thing is though, it was like this with my Keihin butterfly carb that I had on there originally too, but I never bothered to do anything about it because it always ran pretty good, except for a little "coughing" through the carb when it was cold. The CV carb runs great though and it hasn't coughed 1 time so far.
    Can you guys give me some kind of rundown on what to change on this carb to make it run richer? It seems like I should have a nice light brown color on my plugs, but I don't. Do I change jets, the needle, both, either one? I should mention this bike has the stock mufflers on it and as far as I know everything is 100% stock.
    I also got an extra needle, P/N 27094-88, Jet Needle XLH 1200, and a low speed jet, P/N 27170-89, Slow Jet #45 883/1200 with this carb when I bought it on eBay. Will these make it run richer?
    Thanks for any help you might have,
    Snyde
    snydley, Jul 14, 2011
    #1
  3. Lucifer

    Lucifer Well-Known Member

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    Lucifer, Jul 15, 2011
    #2
  4. chucktx

    chucktx Moderator Staff Member

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    plugs sound ok. nearly impossible to read plugs with all the additives the govt. it throwing in todays gas. no coughs, no stumbles, no dead spots.....sounds like your good to go......check fuel mileage....should not increase much, if it does, it could be just a bit on the lean side.
    chucktx, Jul 15, 2011
    #3
  5. hotroadking

    hotroadking Super Moderator Staff Member

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    Yep skip the plug reading, it's just not valid
    except in the case where the plug is black soot covered or oily...

    If you want to richen up the carb you need to remove the bowl
    and check the sizes of the jets, go up one size on the pilot, it's where
    you spend most of the time, and you can go with a thinner needle
    for the needle jet which will allow more fuel from the main.

    However if you are getting decent mileage, and it's not pinging or
    running too hot. Why mess with it...
    hotroadking, Jul 15, 2011
    #4
  6. snydley

    snydley Active Member

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    The plug looks exactly like the "normal plug" picture at this website. I guess I won't worry about it then. I was a little concerned because it's been very hot here in western N.Y state lately, in the 90s, and I was afraid of running the engine too lean and possibly damaging the engine. It's not "pinging" or "stumbling" or anything, in fact it runs much better than the other carb I had on there, the best it's EVER run.
    Thanks,
    Snyde
    snydley, Jul 15, 2011
    #5
  7. snydley

    snydley Active Member

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    I didn't know about the additives, hmm. It runs the best ever though, that's why I posted a message here first before "diving right in" and replacing parts. I've learned I can't fix something that ain't broke no matter how hard I try. :D I'm not sure about the mileage 'cause I didn't think to check it with the old carb on it. I'll run a tank through it anyway and figure out what kind of mileage I get.
    Thanks,
    Snyde
    snydley, Jul 15, 2011
    #6
  8. snydley

    snydley Active Member

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    I'm gonna run a few more tankfuls through it and then read the plugs again. I really hesitate to do anything to it since it running so well.
    Thanks,
    Snyde
    snydley, Jul 15, 2011
    #7
  9. hotroadking

    hotroadking Super Moderator Staff Member

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    JMO leave it alone, maybe put in a bottle of octane boost with your super unleaded if you have that Ethanol crap up there, it's hard on smaller engines...
    hotroadking, Jul 15, 2011
    #8
  10. kenfuzed

    kenfuzed Administrator Staff Member

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    Already great advice posted here from the others but I'll just add that richer doesn't always equal better performance. As the old saying goes, if it aint broke... you know the rest :D

    Without knowing the original jetting size or what needle is installed I wouldn't speculate what needs to be replaced, but once again if the bike is running strong and not hesitating off idle then it's likely the carb has already been taken care of. The 27094-88 (N65C) sportster needle is very good, especially if you are experiencing any off-idle lean hesitation. That needle uses a single taper that comes in much earlier (and richer) than most needles and I would only use it if I believed that a lean condition existed just off idle or in the lower midrange. A #45 pilot would be a fairly standard pilot jet recommendation but it could already have that installed.

    As much as I like to have people buy my parts (CV Performance) I don't advocate part replacement unless there is a specific problem or condition you are seeking to change. If you still need to fine tune the mixture setting here is a brief article on do that:
    Harley CV Carburetor mixture tuning using an EZ-Just
    kenfuzed, Jul 15, 2011
    #9
  11. HarleysLR

    HarleysLR Active Member

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    like everyone else is saying snyde, it sounds good, if you do feel you need to change something I'd start with the needle, 27094-88 (N65C), like Ken said it'll richen it up just a little without changing any jets, that is what I have in both my carbs and it works very well. I don't rely on plug reading, it took several thousand miles just to get any color at all on my plugs.

    Oh yea and hang on to that 27094-88 (N65C) needle if you don't use it, they are hard to come buy now days. or I'll take it off your hands just to have around.
    HarleysLR, Jul 15, 2011
    #10
  12. whacker

    whacker Active Member

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    You might want to check out CVP (on this page)..I bought my CV carb from Kenfused and I couldn't be happier with it...
    whacker, Jul 16, 2011
    #11

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