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Thread: R90S carb parts/advice

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  1. #1
    Registered User kwb210's Avatar
    Join Date
    Jul 2009
    Washington, the state

    R90S carb parts/advice

    I've done a bunch of Bing's and enjoy fussing with them to make them purr. I am working on getting a '76 R90S that has low miles and has not really been ridden much for since 1999. Tires are DOT dated 1999 and look like new (although I would never run on them more than around town during tuning etc.) he says he has only run it maybe 1,000 miles, I would agree with that after looking at the tires etc. Bike starts up but needs to run at 2,800 to about 3,300, just runs kind of choppy, not smooth until the higher RPM then she smoothes out nicely, not happy at an idle. While I can spell Delloto I can't yet pronounce it....where should I look for a carb rebuild kit and tuning advice for the 90S series? Cool carbs btw. I am assuming the rubber O rings got to have ended their life some time ago, any other parts that should be replaced while still staying in the stock mode? My plan at this point if I buy it will to freshen it up and enjoy it on short rides as I have a slash 7 that loves me best when away from home. She and I have something.
    1977 R100/7 1971.1972.1972.1973 R75/5
    1974 R90/6 multiple boxes
    Airhead Revival
    "Objects in the mirror appear to be losing" unk

  2. #2
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    San Antonio, TX
    Check my Sig line for a link to an R90S forum. Also, there's an R90S area at:
    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
    Registered User toooldtocare's Avatar
    Join Date
    Mar 2008
    DeLand Florida
    When I rebuilt the Dells on my old R90S, I got my parts from Rusty at Max BMW. They had a rebuild kit.

    The carbs are not bad to rebuild, two weak areas though. The nut on the float bowl bottom is easily stripped and hard to find a replacement. It has cut-outs in the threaded area to allow gas to flow to the main jet. The accelerator pump works on a plastic lever riding in cut-out of the throttle slide, it can be broken easily. The lever pushes against the accelerator pump. Do not mess with the adjustment on the accelerator pump, just replace any parts needed, such as the rubber pieces. Once rebuilt, adjusting them is the same as any carb, and they hold their synch pretty well.

  4. #4
    Registered User
    Join Date
    Jul 2010
    Tularosa, NM

    dell O'rto Parts

    Good people, excellent service. All parts available for dells:

    Herdan Corporation
    43 Penn Street
    Port Clinton, PA 19549

    Love them carbs.

    Walking Eagle

  5. #5

    Rebuilding Dellortos

    I rebuilt the Dellorto's on my 1975 R90S with rebuild kits from Bevel Heaven in California. Steve at Bevel Heaven also carries beautiful billet "bolts" for the bottom of the float bowls. I also replaced the floats as the old floats don't do well with gas that has ethanol. A couple of tips I'd pass along are: 1) to find a small ultrasonic cleaner and clean the carb bodies for hours to clean out the tiny inner passages, and 2) make sure you set the float height correctly for the Dellortos you have by bending the tab that contacts the needle-seat assembly. 3) make sure you notice which of the three indents the long needle is set to as you open up the carbs.

    1975 R90S
    2000 R1100RT

  6. #6
    Registered User
    Join Date
    Jul 2010
    Tularosa, NM

    dells. . .

    You can also BOIL the carb bodies in distilled (or reverse osmosis) water for at least 30 minutes to clean all the passages. Don't do this inside, unless you're single, as the aroma might not please everyone -- only Airhead fanciers. I bought a big pan at Goodwill specifically for the purpose, and use my outdoor (electric) grill as a heat source. Learned this trick from Randakk, a Goldwing/Honda guru.

    Float height: I just pass this along, because I found it SO strange. When I disassembled the dells, I found the float-height adjustment to be WAY out, and wondered about it. After a cleaning, I VERY PRECISELY re-set floats to factory spec, and NO GAS would flow, at all (!) I ended up bending the tabs back to approximately where they were -- just took a "stab" at it so the bowls would fill, and was good to go. NO LEAKS from the carbs, and the bike goes down the road real good.

    I guess I should add that these dells are mounted to a 78 R100RS Motorsport, so YRMV, due to a possible difference in mounting angle, etc.

    Walking Eagle

  7. #7
    No longer a member here
    Join Date
    Apr 2006
    Looks like there are a couple of experts on these carbs. However, I have not seen one correct, I can once again be a smart aleck:

    Having worked on both R90Ses and R100Ses, the best thing one can do to a R90S in my opinion, is, to change the pumpers over to Bings. The bike will not suffer, as far as street performance is concerned.

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