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  1. #1
    CB750 Member llibellen's Avatar
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    1978 honda cb750k carbs

    I've been working on these 4 carbs since early summer. I bought a 4 carb rebulding kit & rebuilt them 3 months ago. When I start it up (only starts with full choke), gas pours out of the overflow (bottom of carbs). I have tried almost everything I can think of, but to no avail. I just ordered (& received) a second rebuild kit, but before I start rebuilding again I thought I'd check in here for help. I know there are a lot smarter people on this forum, so can someone help me please! Thanks, Bill

  2. #2
    CB750 Guru amc49's Avatar
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    If they run ethanol in your local fuel and the bike sits, then you can have that issue if bike sits as little as a week, the ethanol lets the needles stick. Past that, poor needles in some of the kits cause many issues like that. Many use cheap Chinese rubber tips that are not ethanol resistant and then they swell out of shape to not seal right.

    If the needle seats in carb body have corroded due to ethanol exposure then you likely never will stop the issue.

  3. #3
    CB750 Member llibellen's Avatar
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    OK Thanks. Adjusted float valves to shut off gas intake, so I'm getting closer. I must not be looking in the right sites since I cannot find the m/m measurement for the floats setting & the screw "turns"for the needle valves. I must be looking in the wrong places. Maybe you could point me in the right direction. Thanks again.

  4. #4
    CB750 Guru amc49's Avatar
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    http://manuals.sohc4.net/cb750k/

    You want the K1-K8 supplement, K8 is a '78 model. Go to the page between page 264 and 276, the manual is somewhat messed up as far as the pagination goes.

  5. #5
    CB750 Member llibellen's Avatar
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    Thanks again & again. I think I can get everything from the K1-K8 supplement that you have provided. I didn't
    want to wear out my (newbie status) welcome, but I appreciate you're reply. I may or not need you in the future, LOL
    Thanks Again

  6. #6
    CB750 Member KRBJ's Avatar
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    The Honda factory manual has a few mistakes. In your case it says the slow jets are not renewable but they ARE and should be removed to clean them.

  7. #7
    CB750 Addict Medyo Bastos's Avatar
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    Try here -> http://www.hondachopper.com/garage/c...carb_info.html


    Sent from my iPhone using Tapatalk

  8. #8
    CB750 Member llibellen's Avatar
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    Click image for larger version. 

Name:	lil-rubbers-20190913_155255.jpg 
Views:	1 
Size:	60.4 KB 
ID:	9112 The supplement doesn't have the carb data that I need. These (attached) rubber washers came with the rebuild kit but I can't
    find any data on where they go. I wish I could leave all this to the pro's but nobody will touch it. All said if it's more than 20 yrs old, forget it.

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