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Thread: Change 76 R90/6 with stock carburetors to 92 GS carbs?

  1. #1
    Registered User tanker4me's Avatar
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    Change 76 R90/6 with stock carburetors to 92 GS carbs?

    The R90/6 has the 1000cc Siebenrock kit installed and Im happy with the stock 32mm carbs low end response. The heads were rebuilt at the same time to stock spec.

    The stock carbs are now due for a rebuild.

    I have been told a pair of 92 GS carbs can be installed with little modification.

    The question is, would the newer 32mm carbs off a 92 preform much differently than the /6 32mm carbs?

    Has anyone done this mod before?
    My hesitation to do it is getting the tuning right.

    Bill
    We are all here for a spell, get all the good laughs you can.
    Will Rogers

  2. #2
    Liaison 20774's Avatar
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    Your guess is as good as any. I'm kinda thinking not primarily because they're both 32mm carbs. Clearly the jetting would need to change. I think the mantra with these bikes is it's a zero sum game. Make a change in one region will result in a change in another region which you might not like. But if the swap is easy enough to do, and you have the GS carbs sitting around, might be worth the "test".
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    P Monk
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    was going to check my Bing Book

    But it must not have survived the Harvy flood. I can't see replacing your carbs with GS carbs would be cheaper than rebuilding your own, but if you called Bing, I am sure they can suggest any jetting changes you should make, and would be more than happy to sell you the required jets. I put MAC whispertone muffs on mine and they suggested the proper needle valve and hit it right on the head eliminating a lean running condition.
    P. Monk
    74 R90/6 (the Black Hole), 2011 R1200RT.

  4. #4
    Liaison 20774's Avatar
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    Duane Ausherman has specs for the Bing carbs on his website:

    https://w6rec.com/bing-carb-specs/
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #5
    B Reams brook.reams's Avatar
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    Quote Originally Posted by tanker4me View Post
    The R90/6 has the 1000cc Siebenrock kit installed and Im happy with the stock 32mm carbs low end response. The heads were rebuilt at the same time to stock spec.

    The stock carbs are now due for a rebuild.

    I have been told a pair of 92 GS carbs can be installed with little modification.

    The question is, would the newer 32mm carbs off a 92 preform much differently than the /6 32mm carbs?

    Has anyone done this mod before?
    My hesitation to do it is getting the tuning right.

    Bill
    Bill,

    IIRC, the choke cable is different between these carburetors as the R90 used the stiff solid inner cable while the '92 carbs use a flexible cable with return spring and so won't work with the stock R90 choke lever. You would need to add the handlebar mounted choke lever and that requires a different left control casting. So, not cheap.

    If it were me, I would stick with stock and rebuild them. But that's just me :-)

    Best.
    Brook Reams.
    Brook Reams - Arvada, CO
    Endeavor to Persevere
    Various Two-wheeled Vices, All BMW || Website: Airhead Rebuild Projects
    2004 R1150-RS||2002 F650-GS||1983 R100RS||1977 R100RS||1973 R75/5

  6. #6
    Registered User Anyname's Avatar
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    I don't know if the same applies to the Bings on a BMW, but I remember that the carbs on 90s Japanese bikes often were made so as to discourage owners from making modifications. Things like jets that in pre-emissions control years were accessably installed with threads ended up being pressed into place or blocked with plugs.
    BMW R bike rider, horizontally opposed to everything...

  7. #7
    B Reams brook.reams's Avatar
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    Quote Originally Posted by Anyname View Post
    I don't know if the same applies to the Bings on a BMW, but I remember that the carbs on 90s Japanese bikes often were made so as to discourage owners from making modifications. Things like jets that in pre-emissions control years were accessably installed with threads ended up being pressed into place or blocked with plugs.
    HI Anyname,

    Well, that's not the case with BING carburetors. You can easily change all the jets at will.

    Best.
    Brook Reams.
    Brook Reams - Arvada, CO
    Endeavor to Persevere
    Various Two-wheeled Vices, All BMW || Website: Airhead Rebuild Projects
    2004 R1150-RS||2002 F650-GS||1983 R100RS||1977 R100RS||1973 R75/5

  8. #8
    Nutfarm
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    Carbs

    I have a R75/6 with 32mm Delortos on it. They've been on there for 30 years. They work well and all parts are available for rebuild.

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