1. Some members were not receiving emails sent from XJbikes.com. For example: "Forgot your password?" function to reset your password would not send email to some members. I believe this has been resolved now. Please use "Contact Us" form (see page footer link) if you still have email issues. SnoSheriff

    Hello Guest. You have limited privileges and you can't "SEARCH" the forums. Please "Log In" or "Sign Up" for additional functionality. Click HERE to proceed.

Carb Identification

Discussion in 'XJ Technical Chat' started by Jon81550Maxim, Mar 22, 2008.

  1. Jon81550Maxim

    Jon81550Maxim Member

    Messages:
    53
    Likes Received:
    0
    Trophy Points:
    6
    Location:
    N.Ontario
    I'm hoping someone can help I.D my carbs.
    Bike is XJ550H V.I.N-- 5K6000471 Canadian bike.
    Outer right side of carb (diaphram horn?) says Mikuni.
    My clymer manual says it's Mikuni BS28. Is this correct?
    Main jet is 112.5 as per manual
    Pilot Jet is 37.5 manual says 35
    Pilot air jet is 170 manual says 70, I'm sure theres a 1 in front of it.
    A difference of 70 to 170 is too far out, isn't it?
    Needle jet is O-8 as per manual.
    I would like to have the carbs "stock".
    I have them torn down for a healthy bath in parts dip. 1 carb at a time.
    Pilot screws came out great. #4 was filled up with crud. Wasn't any caps.
    3 Pilot jets came out good but one was de-winged.
    I took a phillips screwdriver from an electronic screwdriver set (really small)and drove it in with a hammer, fairly gently, then used vice-grips
    on it to turn and it worked great.

    Thanks Rickcomatic, that trick with the liquid elec tape did a great job, the
    diaphrams stayed nice and flexable. :D
     
  2. BlueMaxim

    BlueMaxim Active Member

    Messages:
    1,986
    Likes Received:
    4
    Trophy Points:
    38
    Location:
    Central Mississippi
    XJCD shows that the carbs are Mikuni BS28. Main jet 112.5 pilot jet .35 main air jet #70, pilot air jet #165. You are not far from stock. The 37.5 pilot jet can be compensated for via the pilot mixture screw. If the bike is running a K&N or similar non stock filter then that is most likely the reason for the pilot jet increase. I would only change the pilot jet if you are experiencing a stumble around 3500 RPM.
     
  3. Jon81550Maxim

    Jon81550Maxim Member

    Messages:
    53
    Likes Received:
    0
    Trophy Points:
    6
    Location:
    N.Ontario
    Thanks for the info Bluemaxim.
    I have to get the XJCD. When I got the bike originally there was a Supertrap 4 into 1 exhaust on it. The guy must have changed the pilot jet for the exhaust change. Still has the stock airbox on her.
    I was worried a little from the frequent mention of the "hitachi" carbs as to
    which model carbs I had.
    So onward and upward :D
     
  4. scribetree

    scribetree New Member

    Messages:
    26
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    San Jose, CA
    Hey, I just joined this site and I'm having some trouble locating schematics for the BS28 carbs. I found some for the BS34, and I'm wondering how different these are. I'm a newbie to this game, but I'm planning on taking my carbs apart to clean them and I'm just wondering if I can safely follow the BS34 schematics for my BS28 Carbs. Help much appreciated. :roll:
     
  5. whistlerwill

    whistlerwill New Member

    Messages:
    1
    Likes Received:
    0
    Trophy Points:
    1
    hey Scribetree, I wanna do the same with my carb (bs28) and i wanna know if you finally found a place where it is all explaned...
    thank you

    82 Yamaha xj550h
     
  6. bigfitz52

    bigfitz52 Well-Known Member Premium Member

    Messages:
    21,283
    Likes Received:
    419
    Trophy Points:
    83
    Location:
    Rural SE Michigan 60 miles N of Motown
    If by schematic, you mean this:

    [​IMG]

    From the factory XJ550R (Seca) book, the "specs" chart is different for the Maxim although the carbs are the same.


    Exploded view, applies to all 550s:

    [​IMG]

    Does that help?
     

Share This Page