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Carb question... Air compensator jets.

Discussion in 'XJ Technical Chat' started by 750E-II_29Rbloke, Apr 11, 2014.

  1. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Just a quick question for anyone with knowledge of carbs. Wondering what function the air compensator jets either side of the venturi ring of our carbs (or lack thereof) perform?

    I ask because I was just thinking on it the other day, since my E-II would not have had compensator jets fitted to it's original (33mm) carbs but the other 750's (with 32mm) have them.

    If I remember correctly they control airflow to the emulsion tube, but I can't quite get my head around if smaller jets would = less air thus richer mixture or if they would = less airflow thus less fuel/air mix thus weaker mixture.

    So really just wondering if anyone could explain how they function, and maybe what sort of conditions they have an effect under i.e. WOT/high revs/low revs/sudden throttle openings or whatever? Cheers for any help :) Keep em shiny side up.
     
  2. FtUp

    FtUp Well-Known Member

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    they just vent the float bowl, not sure if they perform any actual fuel/air metering functions.

    CN
     
  3. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    I'm not sure we're talking about the same thing here :?
     
  4. KrS14

    KrS14 Active Member

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  5. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Hmm yes, they do appear to be labelled as that on the Mikunis but I'm struggling with the concept that they're only vents on the Hitachi's else Yamaha wouldn't have spent money on fitting the compensator jets to some bikes surely?

    I'm fairly sure their drillings are tied to the emulsion tube/needle jet holder, but other than that I'm unsure of the exact effect they have.
     
  6. wink1018

    wink1018 Active Member

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    Those regulate the amount of air to be mixed in the main and idle fuel circuits. (Emulsion) I played with different air/fuel jets for a while after I installed pod filters. I cannot remember the exact numbers off the top of my head, but I finally was able to properly tune my carbs without sacrificing drivability issues or holes in the fuel delivery to the motor.
     
  7. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Not the ones under the hat (pilot & main air) the ones in the mouth (venturi ring) :( They're called air compensator jets as I recall. Thanks for the reply though.
     

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