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BS38 CV Carbs

Discussion in 'The Garage' started by koyuga, Aug 14, 2017.

  1. koyuga

    koyuga XS650 Enthusiast

    These are the carbs came with my roller wreck.(already stripped and cleaned)
    I guess its an Aussie 79 special.

    Do these carbs normally use a 2-1 cable mount. I read somewhere that a CB350 Cable is sufficient.

    Would anyone have a picture of the main jets and pilots. As I wish to purchase some larger ones.
    I asked the guy who stripped them but he forgot.

    Cheers

    koyuga IMAG0006.jpg IMAG0006.jpg IMAG0009_1.jpg
     
  2. weekendrider

    weekendrider Iron Horse cowboy Top Contributor

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    As oem the independent carbs used a double pull/dual cable throttle assembly instead of a 2 to 1 cable. I think those may be the 74-75 carbs. More info to be found in the "tech" section as to jet sizing. Remember to work with the carb year not the bike year.
     
    gggGary likes this.
  3. 5twins

    5twins XS650 Guru Top Contributor

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    Yes, those look like '74-'75 carbs. They use what's called the "small round" type Mikuni main jet, part #N102/221 .....

    [​IMG]

    Pilots are the BS30/96 style with the metering orifice on the bottom. The VM22/210 style is similar and will screw in but are not correct for your float bowl .....

    [​IMG]

    You'll need to check the sizes in there as many of these have been messed with and changed over the years. Here's a chart with the stock sizes .....

    [​IMG]
     
    gggGary likes this.
  4. koyuga

    koyuga XS650 Enthusiast

    Thx for your replies.
    My bike buddy recommends to fit the carbs and test run it. The reason I ask about jetting is that the pipes are a custom pea shooter 1.5" X 34"
    Plus it will be running unipods.
    My mikuni supplier wanted a photo of mains to Id them.
    From what I read these should be 135 mains, but I may need larger.
    Cheers.
     
  5. 5twins

    5twins XS650 Guru Top Contributor

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    Stock for your carb set would be 127.5's. 135's would be 3 sizes up and could be about right. Only testing will tell you for sure.
     
    gggGary likes this.
  6. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    Looked at a pic you posted of the bike. it is an 80SG should have 3W6-****** as the vin prefix, can tell from the disk brake on the rear, separate regulator and rectifier, clip on seat and points ignition These carbs are from a 74TXA/75XSB. Your bike would have come out with BS34's and they would be a way better carb, 34's have a single throttle cable makes for easier carb tuning........................ so you will need to find the twin cable setup for those carbs
     
    gggGary likes this.
  7. weaselbeak

    weaselbeak XS650 Junkie

    I've had BS34's and BS38's both, 34's pull better down low, 38's better up top. Both were equally decent stuff.
     
  8. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    Remember weaselbeak your 34's are restricted from the factory.

    XSs's had 6 different sets of BS38's over the years and all of them had different jetting needles/needle jets.............Only one set of BS34's..........

    Oceania BS34's have the so called Canadian Needles, (i prefer to say the non US BS34's as the US it seems are the only country to have the non adjustable needles), and Needle Jets.........These pull better than the US EPA mandated 34's
     
    gggGary likes this.
  9. xjwmx

    xjwmx It's just the unknown. Top Contributor

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    Nearly snapped my neck.
     
    gggGary likes this.
  10. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

  11. XS650D

    XS650D XS650 Junkie

    Noticed some conflicting info with above chart for 76/77 Model year Pilot Jet. In chart on Misc column
    it states that 1970 thru 1977 use BS30/96 style Pilot Jet BUT at the bottom under the chart it states
    that 1976-1979 Carbs use VM22/210 Style Pilot.Can someone please confirm which is correct.Thx
     
  12. 5twins

    5twins XS650 Guru Top Contributor

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    The '76-'77 carbs use the VM22/210 style pilot. If you look in the pilot jet column, you will see the entries for the '76-'77 and '78-'79 carbs marked with an asterisk. In the Misc. column, you will see the asterisk denotes the VM22/210 type pilot. It was difficult for me to figure a way to show this when I made the chart and that asterisk was what I came up with, along with the note at the bottom.
     
  13. xjwmx

    xjwmx It's just the unknown. Top Contributor

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    Are these really left-hand thread?
     
    TwoManyXS1Bs likes this.
  14. 5twins

    5twins XS650 Guru Top Contributor

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    No, they are a normal direction thread, but that drawing does seem to show them reversed. Should look like this .....

    [​IMG]
     
  15. XS650D

    XS650D XS650 Junkie

  16. xjwmx

    xjwmx It's just the unknown. Top Contributor

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    Fixed original if you want it :


    9C7Lzro.png
     
  17. 5twins

    5twins XS650 Guru Top Contributor

    19,996
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