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  1. #1
    CB750 Member ChopSticks's Avatar
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    69-76 carbs how can you tell if they need to be cleaned, rebuilt, or replaced?

    Just adopted an orphan 74', multiple foster homes, no records, last one didn't winterize it properly. While I wait for certain tools to come in I figured I'd pull the carbs and clean them. Prior to pulling the throttle was very stiff to open/close, since these models have to dual throttle cables does that mean they don't flick close, and need to be manually closed also? With the carbs off and released from the throttle cables, it's almost impossible to get them to open, I'm assuming these are gonna need to be more than just cleaned? How can you tell the severity of the carbs conditions and the best solution?

    Full disclosure: This is my first vintage bike I've had other bikes prior and but they were EFI, and I did regular maintenance such as fluid changes and minor body work. I've also picked up the service manual just waiting to print it out on Monday

  2. #2
    Moderator dirtdigger's Avatar
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    If the throttle wont open easy then they need cleaned. They have a "heavy" throttle by todays standard but they should open and close smoothly. More then likely the fuel has turned to varnish causing sticking and passages inside are plugged. Pull them and clean them.

  3. #3
    CB750 Member ChopSticks's Avatar
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    Thanks, I just pulled them a little while ago, is there any specific type/brand carb cleaner I should use? Currently trying to put a cart of things I'm gonna need

  4. #4
    Moderator dirtdigger's Avatar
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    depends on how bad they are. If they are bad you will need to get the gallon bucket what you can soak the body in. If they are not to bad you may get by with the spray can type. You will need a air compressor to be able to blow through the passages and the jets to get the stuff out after soaking.

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  6. #6
    Moderator dirtdigger's Avatar
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    use the chem dip if they look pretty bad. Then follow up with some of the spray cleaner. The chem dip is some nasty stuff so you may want to get some cheap rubber gloves to handle the parts after you take them out of the stuff. Chem dip will eat rubber parts so make sure to fully disassemble the carbs if you are going to use it.

  7. #7
    CB750 Member ChopSticks's Avatar
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    That's the thing how can I tell if they "look" bad? You wouldn't have any picture examples of what to look for? Also, the gaskets on the bottom, float bowls, and rubber covers on the top are the only rubbers? Or should I be disassembling the whole thing?

  8. #8
    You got o-rings in the passages between the carbs as well as "above" your main jet seat jet (not sure of the correct term here) and above the a/f screw if I'm not mistaken. DD will correct me if need be. So yeah, to dip you need a full disassemble.

    I had mine ultrasonic washed. No need to fully disassemble then. Just pull float bowls, slides, all jets and visible gaskets. Worked great on mine and they were really gummed up from old gas.

    Good luck on this. Let us know how it goes!
    Everybody has a plan. Until they get a bee in their helmet.

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  9. #9
    CB750 Member ChopSticks's Avatar
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    Geez as I read more and more sounds like ultrasonic is the way to go. Well I just got the gallon of berrymans in, can you tell me what conditions these looks like?

    http://m.imgur.com/a/begBs

    I've watched a few videos and they all have the air slides, sliding back into place smoothly, mines don't move at all and when they throttled were connected it took a little while for the throttles to snap back does this have to do with the double throttle set up?

    Also are the float bowls considered plastic and should not be hit with carb cleaner? One of the floats seem to have lost its springiness also just wanted to know if this is gonna need a full disassemble and dip or just carb spray?

    Lastly any idea what those two tubes in the middle are?! I know the outer ones are the fuel lines but I can't find the middle ones anywhere in the manual

  10. #10
    Moderator dirtdigger's Avatar
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    I have only used carb clean for 20 years never had the need to get a machine for ultrasonic cleaning. Sure it does a great job but can you afford a machine? Nothing wrong with carb dip if you let the soak.

    you carbs dont look that bad. The float bowls are aluminum. You need to take the floats out as well as the jets and the needle and seat. I would dip them, it does the cleaning, then use the spray cleaner for misc. parts that cant be dipped.

    The two tubes in the middle are bowl vents.

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