Settining low speed A/F ratio screws

Discussion in 'Carb/Tuning' started by 98Redlne, Mar 26, 2012.

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  1. Mar 26, 2012 #1

    98Redlne

    98Redlne

    98Redlne

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    Where the heck is the procedure for setting the A/F screw positions? I know that a dyno or an A/F meter is the best way, however I thought I recall a procedure to get you close for those without access to these resources.

    Since waking the bike up after it's long winter nap I have had a backfire/stumble during decel and when running at low throttle positions.
    The bike starts and idles well but when moving the constant backfire is fricking irritating (it is also hard to look cool when your bike sounds like Chitty-Chitty-Bang-Bang).

    Did both the shotgun and peashooter this weekend. I didn't catch any significant particles or massive gunk in any of the circuits but what did come out was really orange in color. Continued to push carb cleaner until it came out clear. A/F screws looked OK, not super gunked up but there was a little goop on the end of the screws. Drained the bowls and the fuel was clean with no particles or sediment.

    Set the A/F screws back to their previous positions but I think that with the circuits cleaned out the ratios might not be what they were before the cleaning.


    sooooooo....anyone got a link to the procedure? My google-fu was weak this weekend.
     
  2. Mar 26, 2012 #2

    sdt354

    sdt354

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    I know this isn't an answer to your question, but how about some good carb cleaner and a fresh tank of gas run through first? How do the carb boots look? Apply some choke when the popping starts and see if that effects it.
    A/f screw usually start out at 2 1/2 turns out and fine tune from there. Mine, with Mark's 4-2, are out 2 3/4 -3 turns out. And, done after a sync.
    Orange fuel is a result of the gas we use breaking down over time. Decelleration diaphrams could be sticking too. I'll think about this more, been there.Me, I replaced all the carb and vboost booots to cure an issue like this.
    Steve-o
     
  3. Mar 26, 2012 #3

    98Redlne

    98Redlne

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    sdt.....been there done that :biglaugh:

    The bike got a fresh tank of gas and a good long ride before I started into the carbs. I wanted to make sure all of the old fuel (StaBil treated) was cleared out before making my assessment of the carbs.

    Part of my checkout was to look at all of the boots and rubber parts. Everything looks great and is clean and pliable, no rips or tears. The bike is a 2007 and only has 2500miles on the clock, garage kept so everything is still in pretty pristine condition.

    The shotgun and peashooter procedures have you remove the airbox and slides and douse the PAJ1 and PAJ2 as well as the Needle and A/F circuits with carb cleaner. I pumped cleaner until what was coming out was the same color as it was going in. Cleaned and lubed the slides and diaphragms (all look good) and buttoned it back up.
    Synched the carbs and it seems much better but I still need to dial in the A/F mix.
     
  4. Apr 5, 2012 #4

    npthayer

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  5. Apr 6, 2012 #5

    naughtyG

    naughtyG

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    The problem is that without an O2 sniffer telling you exactly what your A/F ratio is, adjusting the A/F screws is simply guess work at best.

    There isn't really any other way to set them accurately. :bang head:
     
  6. Apr 6, 2012 #6

    PDWeyand

    PDWeyand

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    If you added an O2 sniffer to the bike and got a/f how would you know your reading in the right place with it first off and second off without fuel injection to change to the reading according to the sniffer, would it just be something extra to have on the bike to mess with. I am not saying that O2 sniffer would not help you know if your running rich or lean but without adjusting it all the time like a fuel injection system would you not going to the most out of the sniffer. Am I wrong in this line of thinking.
     
  7. Apr 6, 2012 #7

    naughtyG

    naughtyG

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    TBH I'm not sure. My understanding is that the A/F screws lets you adjust your air/fuel ratio for each cylinder, and unless you have the means of reading what the actual ratio is (which an O2 sniffer should give you and shows on dyno runs - they just put the probes in your exhaust), you're basically in the dark and guessing when turning your A/F screws.
     
  8. Apr 6, 2012 #8

    gamorg02

    gamorg02

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    what do you mean 'right place'?

    thats exactly it. if you don't have bungs my tuner put a long copper tube off of the o2 sensor as far as he could go towards the front header then ones that was tuned he bent it as much as he could and adjusted the tube towards the rear cylinder on that side and adjusted the carb accordingly.

    i have bungs now and am considering getting one for the a/f tuning and potentially just mount it up. innovate has some all in one widebands on ebay for like $160.

    i imagine those same ones could be set up with some copper tubing like my tuner did for those without bungs.
     

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