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Thread: 32mm Flat Top Carb Rebuild

  1. #1
    Mike V. #30064 30064's Avatar
    Join Date
    May 2006
    San Diego, CA

    32mm Flat Top Carb Rebuild

    Just wanted to share some interesting photos after rebuilding my 32mm Flat Top Carbs after many (too many) years. First of all; I was hesitant to rebuild the carbs due to how well I "thought" the bike (78 R100/7) was running. It wasn't blubbering, stalling, or non-responsive at all. Smooth throughout all throttle transitions. On the average, my mileage was in the range 38 to 45 mpg. I knew the left carb mixture jet was not responding to adjustment but the mileage and performance of the bike was excellent if you were to ask me. Maybe after so many years I became a bit conditioned to it's general slowly degrading performance. I've never experienced so much gum and buildup inside my carbs, obviously a result of the gas we are receiving these days. The jet stock, needle jet and atomizer were covered with a syrup type of buildup.

    By the way, the UC-20D Ultrasonic Cleaner is the only way to go. An intial 30 minute soak at 40??C with a 50/50 Simple Green solution and water brought an amazing amount of crap radiating from the body and associated parts. Then two seperate clean water rinses in the ultrasonic cleaner at the same time and heat level gave the bits a very high quality wash and cleaning. I highly recommend this method for the complete Bing service.

    Left Bing (64/32/223):

    Right Bing (64/32/224):

    Looking forward to the results of my labor after new 52mm carb collars, new choke cables and Viton fuel line arrives.

    It was pretty nasty in there with horrible condition of o-rings. All o-rings were either cracked, split, turned to mush or all of the above.

    -Mike V. / San Diego
    Mike V. / San Diego
    MOA#30064 / ABC#11027
    78 R100/7 [orig. owner] / 81 R65 [restored]

  2. #2
    Registered User
    Join Date
    May 2012
    Here is another link (without the business):

    It seems most people like mixing up something to pour back into the sink. I prefer using Chem-Dip by Berryman:

    Loosening the top screws, taking off the carburetor, removing the cable attachments (whilst leaving the cables with the top), then removing the top and leaving it with the bike is an easy way to remove the carburetor for cleaning. The top can be cleaned with a paper towel and carburetor cleaner while attached to the cables.

    In this condition, removing the diagram and slide with needle leaves the carburetor body. The float bowl and floats are removed before putting the body in a Chem-Dip basket and immersing. Soaking in the Chem-Dip is an easy way to clean the jets and passages along with the outer body. The float bowl can be similarly cleaned or put in the basket with the carburetor body.

    As always, use common sense, read the MSDS of the products, and wear protective gloves in an area with adequate ventilation. The new formulation of Chem-Dip has been generally considered inferior to previous (high aromatic hydrocarbon) products, but I find it works just fine with more soak time.

    Of course, all this does is clean out the varnish and build-up before replacing parts. Any leaking o-rings or gaskets have to be replaced.

    AH# 13238

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