#38 pilot jet plugged solid (cb500t)
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  1. #1
    jml
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    #38 pilot jet plugged solid (cb500t)

    I found this in one of my carbs tonight; it's so solid that it looks like it never even had a hole bored in it (it is open at the other end and crossways in the middle, like the jet from the other carb). It's currently soaking so I can see if I can open it up tomorrow, but there's not some weird scenario where it's supposed to be this way, is there? This is the carb with the choke on it.

    #38 pilot jet plugged solid (cb500t)-_20190915_185135.jpg

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    Senior Member WintrSol's Avatar
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    have a look at the pilot jet (PJ) on this drawing, and see if it isn't the same:
    #38 pilot jet plugged solid (cb500t)-carb_schem.jpg
    Rick

    Mine is a mostly 1970 CB450K3

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    jml
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    Quote Originally Posted by WintrSol View Post
    have a look at the pilot jet (PJ) on this drawing, and see if it isn't the same:
    Click image for larger version. 

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    Huh. That is exactly what it looks like, I'm glad I asked. The pilot jet in the other carb does have a hole through the end, does that mean it's wrong, or is it actually supposed to have it? There's no context on that drawing, so I don't know if they're supposed to be different.

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    Senior Member WintrSol's Avatar
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    The carbs should be identical in all the important ways. The pilot jet gets fuel through the main jet. If the other carb is different, it is either not the same type, or someone has put the wrong jet in. The carb number should be stamped into it, somewhere.
    Cal likes this.
    Rick

    Mine is a mostly 1970 CB450K3

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    jml
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    Quote Originally Posted by WintrSol View Post
    The carbs should be identical in all the important ways. The pilot jet gets fuel through the main jet. If the other carb is different, it is either not the same type, or someone has put the wrong jet in. The carb number should be stamped into it, somewhere.
    That is the most logical scenario. Unfortunately I don't know the history of this bike, so I have no idea what was done to it over the years, which means I wasn't sure which way was right. Thanks for clarifying!

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    Senior Member tbpmusic's Avatar
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    There should not be a hole in it through it's length.
    And, as pointed out, all fuel passes through the main jet first.
    Bill Lane
    Honda Twins Founding Member

    No advice, just info

    '75 CB200T, '71 CB450 K4 Half-Breed, '72 CL350 (Sold), '81 CM200T, '72 C70M
    and a little red Chineeze scooter

    http://www.bikeexif.com/honda-cb450-restoration

  8. #7
    Senior Member WintrSol's Avatar
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    For the standard carbs, there is no hole at the bottom, but some will feed directly from the bowl; the number stamped on the carbs may tell that story.
    Rick

    Mine is a mostly 1970 CB450K3

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    jml
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    I went out to compare and here's what I found. The pilot jet without the hole is a #38 with a manufacturer's mark on it, and is in a carb body stamped "NF<illegible> 751A". The pilot jet with the hole through it is also a #38 and has the same marking on it, and is in a carb body stamped "NFL 751A"; this is the carb with the choke lever (I may have gotten that part backwards earlier). Does this help clarify anything?

    #38 pilot jet plugged solid (cb500t)-_20190916_135618.jpg#38 pilot jet plugged solid (cb500t)-_20190916_135709.jpg

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    Sensei 66Sprint's Avatar
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    THEORETICALLY, it makes no difference WHERE or HOW the fuel enters that jet.....
    It ONLY matters that the orifice size of that jet is correct to control the flow speed/volume of the fuel that passes through it.....

    HOWEVER, in a 450 carb, IF the jet (threading) is NOT long enough to extend up beyond the transfer passage from the main jet, then the flow speed/volume is being controlled by the passage diameter, NOT the jet.......

    I have a spare #38 450 style "plugged" jet I'll gladly donate if you'll cover the mailing expenses........Phone me at number in red below......
    WintrSol and jml like this.
    "I have a mind like a steel trap.....Old and rusty, of antiquated design, and hard to get stuff back out of...."
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  11. #10
    Senior Member WintrSol's Avatar
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    Looks like someone has used an engraving tool on the letters of those carbs; the numbers are undamaged, anyway. I've never had a 751 type to take apart; anyone know which type jet is supposed to be in a 751 carb? Or if it has the transfer passage from the main jet?
    Rick

    Mine is a mostly 1970 CB450K3

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