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Thread: Mikuni BS32ss oring list

  1. #1
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    Default Mikuni BS32ss oring list

    Is there a definitive list of oring sizes needed for rebuilding a Mikuni BS32ss from a GS650/GS550? I've looked but haven't been able to find it. My hard parts are all pretty good (except for bodies mentioned in other threads), so I'm trying to buy just the needed orings. I like to buy in bulk from grainger, which turns out to be cheaper than individual items, and then you have left overs.

    I normally use jetsrus, but their list of Mikuni orings doesn't mention BS32ss. The service manual also does not have a list in my scan.

    Looking at my parts and the various fiches, a starting list is below. Is there a better source? If not, does anyone have the sizes? Else I'll just measure the ID's and estimate the cross section diameter.

    Note - I'll update this list as more info comes in.

    Item - Qty - Size
    Intake manifolds - 4 - 38(?)x2.4
    Float bowl drain - 4 - 5.1x1.6
    Needle valve seat - 4 - ?x?
    air mixture screw - 4 - ?x?
    fuel transfer tubes - 8 - ?x?
    air vent T's - 4 - ?x?
    Choke plunger - 4 - 10x1.5

    Did I miss any?

    Thanks
    Last edited by sacruickshank; 12-08-2021 at 10:26 AM.
    Current rides: GS650L, GS550T, GL500, GL1100, Bonnie, Triumph Adventurer, Guzzi California

  2. #2
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    All you need to know is in this thread.....

    https://www.thegsresources.com/_foru...es-as-promised
    1978 GS1085.

    Just remember, an opinion without 3.14 is just an onion!

  3. #3
    Nessism's Avatar
    Nessism is offline Forum LongTimer GSResource Superstar
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    All the various sizes (intake boot O-rings excepted) are listed in the carb rebuild tutorial linked in my signature...

    o-ring size.jpg
    Last edited by Nessism; 12-08-2021 at 10:35 AM.

  4. #4
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    Quote Originally Posted by Nessism View Post
    All the various sizes (intake boot O-rings excepted) are listed in the carb rebuild tutorial linked in my signature...

    o-ring size.jpg
    Perfect, thanks. The link provided earlier seems to have been edited, which makes sense since the poster seems to be going thru some health issues.
    Current rides: GS650L, GS550T, GL500, GL1100, Bonnie, Triumph Adventurer, Guzzi California

  5. #5
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    Here's the table as I've collected from the various sources. The only remaining gap is the air vent T's which are close to the fuel transfer tubes in size and don't seal any fuel, so precision isn't as important.
    Item Qty Size AS568 size
    Intake manifolds 4 38x2.4-2.6 -128
    Float bowl drain 4 5.1x1.6
    Needle valve seat 4 7.1x1.6
    air mixture screw 4 2.7x1.13
    fuel transfer tubes 8 6x1.8 -010
    air vent T's 4 same as fuel transfer?
    Choke plunger 4 10x1.5
    CV Inlet (?) ? 7.65x1.63 -903
    Current rides: GS650L, GS550T, GL500, GL1100, Bonnie, Triumph Adventurer, Guzzi California

  6. #6
    Nessism's Avatar
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    Yes, the vent Tee O-rings are the same size as the fuel Tee and transfer tube O-rings.

  7. #7
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    Quote Originally Posted by Nessism View Post
    Yes, the vent Tee O-rings are the same size as the fuel Tee and transfer tube O-rings.
    Thanks. My fuel T is rubberized, so no orings. Still feels rubbery, not hardened, so I plan to re-use.
    Current rides: GS650L, GS550T, GL500, GL1100, Bonnie, Triumph Adventurer, Guzzi California

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