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Is this the right pilot jet.

Discussion in 'The Garage' started by chaine noble, Nov 12, 2017.

  1. chaine noble

    chaine noble XS400 Member

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    Hello all. Ive been trying to fix a common problem with xs400's. High rpms at idle. I've read and tried so many post suggestions to no avail.ive read this morning the it might be athe pilot jet size ao i took it out and it says 42.5 so its correct. The only this is when i google 42.5 pilot jet for bs34. Its different that mine.they have holes in the side and mine has one tiny hole in the bottom. Heres a pic and its a 79 xs400 d i beleive.

    Thanks...glen
     

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  2. BBS360

    BBS360 XS400 Guru

    Jets for BS34s will vary depending on the bike they are installed on.

    Edit: Misread. Incorrect jet.
     
    Last edited: Nov 13, 2017 at 11:27 AM
  3. NewHavenMike

    NewHavenMike 1976 XS360C

    Well, what have you tried so far?
     
  4. BBS360

    BBS360 XS400 Guru

    And what have you done to the bike?
    Aftermarket intake or exhaust?
     
  5. xschris

    xschris miles of smiles =)

    Wrong style jet. The sohc xs400 jets should have holes on the sides also know as bleed jets. Yours looks like it's from a VM carb that uses non-bleed screws.
    DSC03289.JPG
     
    BBS360 and 16VGTIDave like this.
  6. xschris

    xschris miles of smiles =)

    Post a pic of the carbs so we can see what your using.
     
  7. chaine noble

    chaine noble XS400 Member

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    The only thing i did is install pamco ignition and install there air filters which i was tikd are a direct replacememt
     

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  8. chaine noble

    chaine noble XS400 Member

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    Heres a pic of the carb
     

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  9. BBS360

    BBS360 XS400 Guru

    Are the hiflos the pleated paper filter type?
    I believe it's been suggested that they allow more air flow than stock.
     
  10. xschris

    xschris miles of smiles =)

    Those carbs are off an 81 model. If they have foam floats they need to be set to 32mm. Also the pilot mix screws come from the factory capped if yours are uncapped they should be set to 3 turns out if everything is stock. If your air filters are paper then tuning the bike will be a bit more difficult as stock ones are foam, which are the best.
     
  11. chaine noble

    chaine noble XS400 Member

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    Kind of a brissol material, but it says on the box " direct replacement for oe filter" and " no need for any carburettor adjustments"
     

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    Last edited: Nov 13, 2017 at 3:04 PM
  12. chaine noble

    chaine noble XS400 Member

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    Heres a pic of the floats. Ive had 4 and even 4.5 turns out..a little better but doesnt fix the problem.should i get the pilot jet with the holes in the side and try that?
    Thanks
     

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  13. xschris

    xschris miles of smiles =)

    Those are the right filters. You need the bleed type jets to make it run right. Make sure the pilot jet rubber plugs are new as well. If the bike is all stock ( posts some pics of it) that should fix most of it. Make sure valves are set and the carbs are synced with a manometer after the bike is warmed up.
     
  14. chaine noble

    chaine noble XS400 Member

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    Thanks guys..heres a pic. I will post more in the gallery. I call it my zombie apocalypse bike :)
     

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    BBS360 likes this.
  15. xschris

    xschris miles of smiles =)

    That's the stock exhaust. Are you also using the stock air boxes with those air filters? What are the main jets in those carbs? They should be 135. Also on the mouth of the carbs there should be 155 air jets in them. Slide needles should be 5GZ9. I ask because with those being off a later bike someone may have switched them for the wrong ones as they did with the pilot jets.
     
  16. chaine noble

    chaine noble XS400 Member

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    Heres the airbox..i will check on the rest. The bike works great at everything but idle
     

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  17. BBS360

    BBS360 XS400 Guru

    Cool bike. Stock airbox. Chris' info should steer you in the right direction.

    Unrelated question, how'd you bolt up the ammo box?
     
  18. chaine noble

    chaine noble XS400 Member

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    There are 2 holes in the frame under the seat. I just used long bolts with spacers , washers and wing nuts. It works pretty good but a bit noisy though..espically the handles
     

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    BBS360 likes this.

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