VB-21B carburator cleaning
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Thread: VB-21B carburator cleaning

  1. #1
    Junior Member kjheim's Avatar
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    VB-21B carburator cleaning

    I have a 1978 Hawk TII with a VB-21B carburetor that I am trying to clean/rebuild because it was sitting for three years with fuel in the carburetor and it runs very poorly. I was able to remove and clean most of the jets and jet needles but am having trouble figuring out how to remove the slow needle jet. It looks like the slow needle jet is pressed in and I'm not sure of the best way to remove it. I'm referring to the jet needle that is normally covered by a rubber plug. Any help/suggestions would be greatly appreciated.
    Last edited by kjheim; 08-28-2019 at 03:51 PM.

  2. #2
    Senior Member knauff13's Avatar
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    There's a really helpful sticky on rebuilding VB carbs here in case you haven't seen it:

    https://www.hondatwins.net/forums/63...-cleaning.html
    Ben Knauff
    1978 CB400A Hawk Hondamatic

  3. #3
    Member mikemo's Avatar
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    Does the pilot (slow) jet have a screwdriver slot in top? Can you take a picture and show us what things look like?

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  5. #4
    Junior Member kjheim's Avatar
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    The photos show the carburetor model number and the pilot jet.VB-21B carburator cleaning-cb400-08-29-19_17-26-55-.jpgVB-21B carburator cleaning-cb400-08-29-19_17-27-29-.jpg

  6. #5
    Super Moderator J-T's Avatar
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    The slow jet is "not removable". It can be done but pretty much always will destroy the jet. The slow jet size is generally not an issue, just ensure it is clean (reference the above mentioned tutorial).
    JT
    81 CM400T

  7. #6
    Junior Member kjheim's Avatar
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    Problem solved. I removed the pilot jets using a drywall screw, a torch, a pair of pliers, and a hammer. They are still in very good shape with a little smoothing on the end using a file but I was able to find replacements and will use those. One was a little clogged so I'm hoping that was my problem. I also noticed some small holes and creases in the air cutoff diaphragms and will replace those as well.

  8. #7
    Super Moderator longdistancerider's Avatar
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    Interesting removal process.
    Where did you find the press in idle jets?
    J-T likes this.
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress


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    Junior Member kjheim's Avatar
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    The website where I purchased the pilot jets is CYCLE-RE-CYCLE PART II New Parts Catalog. I haven't received them yet but they are indicated to be for "Various KeiHin VB Style Carbs" and the measurements are correct. If they don't work out the originals are in good enough shape to reuse. Also, found a great paper describing the function of the air cutoff and the removal of the pilot jets at:

    https://www.motorcycleproject.com/te...hite_paper.swf

  10. #9
    Super Moderator longdistancerider's Avatar
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    It looks like those will work. Let me know.
    Mike Nixon's white papers are in .swf format which won't work with Google Chrome. I'll have to open another browser and see
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress


    https://www.hondatwins.net/forums/22...d-attempt.html and https://www.hondatwins.net/forums/1-...r-attempt.html
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