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carb problem or engine problem

Discussion in 'Motorcycle Tech Talk' started by crazyrider, Jul 17, 2016.

  1. crazyrider

    crazyrider Member

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    ok guys i have a nighttrain with the s and s motor was coughing,backfiring when i let off gas i changed every part in carb still same problem checked for any leaks none i raised the carb slider needle seemed to help for 1 day now same issue carb has been cleaned ,also the day i moved the slider needle when bike got hot i shut it off
    and bike trys to run a little then sneezes,also my pipes are turning blue bad,im about to toss a rag in tank and burn it ,replaced slider,air mixture,idle screw,manafold rubber,float needle,
    please any help would be great
  2. Red Rider

    Red Rider Well-Known Member

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    Sounds a whole lot like a vacuum leak. Sometimes it is on a line in a spot that isn't easily seen. When did it start, out of the blue or after work was done? Do you have the original CV carb? If so, you could swap it out and eliminate that. Backward needle problem?...though that could only happen after you did the carb work, and I'm not even certain that can happen with an S&S carb (not an S&S user). Don't burn it just yet...still more to check first...like are your pipes tight at the engine? Good luck!
  3. Lucifer

    Lucifer Well-Known Member

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    A little more info might help...How big an sns motor?? Sns carb or stock CV??
  4. crazyrider

    crazyrider Member

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    90cc sns motor cv carb i got all parts from this site i got thinking i got bike in arazona a custom build i currently have it in maine maybe its the climate
  5. crazyrider

    crazyrider Member

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    when i raised the needle in slider poping and sneazing went away but sat for 1 month now its poping ans sneazing like it use to
  6. Red Rider

    Red Rider Well-Known Member

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    Not the climate. CV carb can handle lots of change. Sure you didn't have any seal/diaphragm leaks? Are you a new owner on this bike? Did the bluing just happen? We're still short on info to help much.
  7. crazyrider

    crazyrider Member

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    had little on it but not much all seals are good

    Attached Files:

  8. Red Rider

    Red Rider Well-Known Member

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    Nice looking ride. Hope you get to ride soon.

    Did it ever run different/better with those same pipes? They're low reversion, and can cause your symptoms. Without more info, though, I'm done guessing.
    :cigar:
  9. Lucifer

    Lucifer Well-Known Member

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    Not familiar with that motor, I know they have complete 80",96",111" and 124"motors...
    I believe it's a fuel problem you have and front cylinder usually runs leaner than the rear, an 80 inch S&S would have different jetting requirements than a 96 inch motor. What jets did you use,and 80" would need a 45 or most likely a 46 pilot jet,which is where you have to start to get it tuned, the mixture screw should give you your best idle between 1.5 and 2.5 turns out from gently seated,less than 1.5 turns,you need a smaller pilot,more than 2.5 turns and you need a larger one, pilot controls idle to 1/4 throttle,the needle meters 1/4to 3/4 throttle and main jet is 3/4 to wide open.
  10. kenfuzed

    kenfuzed Administrator Staff Member

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    Hi crazyrider, I suspect that the problem is related to clogged passages in the carburetor. There is a 3-way passage that connects the idle circuit (pilot jet) to both the front air intake port and the mixture screw metering passage. These commonly get congested if fuel is allowed to sit for any period of time. You need to remove the pilot jet, mixture screw, and mixture screw packing (spring, washer, o-ring) to clean this properly but it can be done with some dish soap and compressed air. Just be careful not to lose those packing parts. This is described under item #3 on the following page:
    https://cv-performance.com/harley-cv-carburetor-tuning-issues
  11. crazyrider

    crazyrider Member

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    thanks for the replys guys im just selling the bike getting a honda harley isnt for me
    thanks guys
  12. Red Rider

    Red Rider Well-Known Member

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    Whatever you get, ya might want fuel injection for your next one...
  13. joshbob

    joshbob Well-Known Member

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    I've seen just as many Hondas as Harleys in Tattoo's repair shop. Hope you have better luck with the Honda.
  14. Lucifer

    Lucifer Well-Known Member

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    So true Josh, if it has (.)(.)s or wheels,it's gonna give you problems;)
    joshbob likes this.

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