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  • Carby rebuild

    I've just started tidying up an old CB250 for my girlfriend to learn on and one of the first things that needs doing is the carby.

    The bike hasn't run well for the last few months and the mechanic that used to service it said it was something to do with the carburetor, I just can't for the life of me remember what he said was specifically wrong with it. My plan is to strip the carby, clean it, replace all the seals, reassemble it and see how she goes.

    However, the carby I've ever played with is the little one off my petrol RC car. Are there any pitfalls I need to keep an eye out for? Will a be needing a manometer/vacuum pump? Its only a single carby so I wont need to balance it.

    Also, should it all turn to custard and I completely make a mess of it, how happy will a mobile mechanic be come and help me sort it all out? I would imagine they wouldn't really appreciate being given a handful of shit to make work again.

    Any advice/comments would be much appreciated.

    Cheers,
    #109

  • #2
    Originally posted by Al_86 View Post
    Will a be needing a manometer/vacuum pump?
    no

    float level needs to be set
    Originally posted by Bendito
    If we get to a stop and we are missing a dozen bikes and you are last, it was your fault. Don't be that guy. No one likes that guy.

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    • #3
      If you are comfortable with tools and pulling things apart, then its worth a carb clean. You need to be careful and methodical, and before removing small parts or jets it is worth drawing the layout as you pull apart. Most jets are numbered with their size and need to be put back in the correct spot. Not many people trying to fix problems later will find it easy to spot swapped jets.

      If doing this, clean the outside of the carb properly, even before you remove it. Dirt on the outside may move around once the carb is apart and is to be avoided.

      If you know the history of the bike, and the history goes back to a time when it was running well, I would do a basic clean and leave the float level alone. For every 12 carbs that need a clean, there is 1 carb that needs a float adjustment (unless someone has played with it first)
      Being an Australian is not an excuse for being dumb and racist.

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      • #4
        *gasp*

        first thing you must do is grab hold of the float rail and starting bending it to compensate for the ageing of the floats bouyancy
        Originally posted by Bendito
        If we get to a stop and we are missing a dozen bikes and you are last, it was your fault. Don't be that guy. No one likes that guy.

        Comment


        • #5
          Being an Australian is not an excuse for being dumb and racist.

          Comment


          • #6
            Originally posted by darkfibre View Post
            If you are comfortable with tools and pulling things apart, then its worth a carb clean. You need to be careful and methodical, and before removing small parts or jets it is worth drawing the layout as you pull apart. Most jets are numbered with their size and need to be put back in the correct spot. Not many people trying to fix problems later will find it easy to spot swapped jets.

            How can you mix up the pilot jet with the main jet ???


            If you know the history of the bike, and the history goes back to a time when it was running well, I would do a basic clean and leave the float level alone. For every 12 carbs that need a clean, there is 1 carb that needs a float adjustment (unless someone has played with it first)
            You have never done this before have you ............


            buelllord
            Women are like motorcycles, they should be ridden hard and kept well lubricated ...

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            • #7
              Originally posted by buelllord View Post
              You have never done this before have you ............


              buelllord
              I can only dig holes, its up to the others to decide that they want to fall in them.
              Being an Australian is not an excuse for being dumb and racist.

              Comment


              • #8
                Dodgy float valves can be a pain in the butt. Not that dear an easy to change.

                With a single carby even easier

                Sent from my HTC Desire using Tapatalk
                Every one has a story.....

                http://www.perthstreetbikes.com/foru...updates-82338/

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                • #9
                  Cheers guys. All very useful advice.

                  I think I should be right. Im not a complete mechanical retard so as long as Im clean and methodical and pay attention to how everything went together, it should come good.

                  If not, I'll be sure to post up with a detailed explanation of just how catastrophically I failed.
                  #109

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                  • #10
                    Cleaning carb=good.

                    Unnecessarily dicking around with float level=bad.
                    -

                    Comment


                    • #11
                      Well, that was easier than expected.

                      I removed the bowl and float first and everything appeared to be sparkly clean. Not a spot of dirt anywhere. All the seals were fresh and in good nick, even the float looked as if it was brand new. The rubbers around the vacuum cylinder and the accelerator pump diaphragm thing looked as if they had been installed yesterday. I very carefully put it all back together clean as a whistle, and cleaned the muck off the end of the choke cable.

                      I bolted it back onto the bike, screwed in two new spark plugs (the old ones were well used), gave it a fresh tank of ultimate and she ran. Better than I recall it running too.

                      I only once managed to elicit a bit of a fart and a backfire or two when I gave it a fist-full from idle, but the choke was all the way out which may have affected it. I haven't got the chain or sprockets on yet so I don't know what it will be like under load.

                      There was a massive amount of muck in the drain line that comes out of where the crank-case breather enters the airbox, but surely that wouldn't affect it at all?
                      #109

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