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  1. #1
    CB750 Member met2's Avatar
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    cb 750 carbs overflowing

    hi all,

    i have a 1972 cb750....a good strong runner at least she was last year.

    i started her this morning after about a year, and she fired up 1st go.

    only thing is, i noticed fuel dripping out of 2 carburetor bowls.
    this flow stops when i turn the petcock of...
    otherwise the bike starts idles and runs beautifully.

    any ideas on where to look 1st...?

  2. #2
    CB750 Addict pidjones's Avatar
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    Either float valve sticking (or junk in the seat), or overflow pipe cracked. To identify the culprit, replace the drain lines with clear tubing. Carbs usually all have to come off to fix, however. You might get real lucky and be able to tap the leaking carb side LIGHTLY with a screwdriver handle and jar a float valve into seating. BTW, specify model when asking for help. Often it helps.
    "Love 'em all.... Let GOD sort 'em out!"

  3. #3
    Moderator dirtdigger's Avatar
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    Quote Originally Posted by pidjones View Post
    BTW, specify model when asking for help. Often it helps.
    It says 72 cb750

  4. #4
    CB750 Addict pidjones's Avatar
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    Were there only Ks in '72?
    "Love 'em all.... Let GOD sort 'em out!"

  5. #5
    Moderator dirtdigger's Avatar
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    yes, engines and carbs are basically the same regardless.

  6. #6
    CB750 Member met2's Avatar
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    im thinking of doing a re-kit on them....

    are the 750 kehin carbs and air filter assembly easy to take out and re install back in place?

    ive been told it is a nightmare
    putting the airbox back on through the frame after the carbs are installed, on some of these old bikes...

    any tricks or anything i need to take note ?

    im thinking of using randaaks gaskets and parts for the job.

  7. #7
    CB750 Addict pidjones's Avatar
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    There is a great rebuild pdf that you really must get. I have found in/out easier with the insulators heated. This also helps to prevent cracking old ones (use heat gun or hair drier). A ratchet strap helps pull them back into the carb insulators, but don't get over-zealous with it. Don't be surprised if you have to go through them several times as there is a lot going on in each carb x 4. On my '79 F (even more complex), it helps to reach in through the airbox to position the airbox-to-carb insulators. Carbs can be disconnected and rotated ~90 degrees to permit much easier access for disconnecting cables, the reverse this going back in.

    The dohc carb instructions are very helpful over-all, but you will need another reference for details as the sohc carbs are much simpler: http://www.cb750c.com/modules.php?na...wtopic&t=13611
    "Love 'em all.... Let GOD sort 'em out!"

  8. #8
    CB750 New Member Ghackett1's Avatar
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    Mine did same thing, I got a very small rubber headed hammer and tapped very lightly on the bottom of all four carb bowls and the overflow stopped and bike ran great, no more leak.

  9. #9
    CB750 Member met2's Avatar
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    thanks to all who replied...

    one more question:

    am i able to get to the float and needles so that i can replace them without
    pulling out the carbs from their mount on the bike.....?

  10. #10
    Moderator dirtdigger's Avatar
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    You need to be able to tip the carbs up side down so you can adjust them/set float level

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