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    • C
      chris last edited by

      Hello,

      does anyone know where to buy a new Throttle-Spring?
      I mean the big one that is at the end of throttle cable and goes into the carb.

      alt text

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      • C
        chris @chris last edited by

        At Mikuni and Yamaha dealers it is out of stock and no longer available😧

        Found a supplier, that has the specs, nearly equal the original spring I hope

        While Im at it, what would you suggest to get for carburetor adjusting
        for a "stock" 4BL that has no more known restricted parts?
        main jets in 230,240,250? others?
        which idle jets?

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        • S
          SpookDog @chris last edited by

          @chris
          I’d look for a kit online. Full range. Why do you want to change the jetting?...

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            chris @SpookDog last edited by

            Hi, I want to change the jets because I dont know whats in there at the moment
            The whole bike was not used for 6 years, it startet after the third kick, but it was idleing at 5000 rpm and I couldnt get it down
            and it was dying with too much gas-pull, also the gas was hanging a bit in the end position

            What is the full range you mean?

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            • Calum
              Calum last edited by

              Sounds like an airleak to me.

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              • C
                chris @Calum last edited by

                @Calum

                That might be possible.
                I didnt check the airfilter before starting the long time sleeper 🤦
                After opening the airbox I found the filter was crumbling apart
                I could image that this was causing it, but wouldnt that mean less air instead?
                Even after opening the carb and realising its not even slightly dirt in there Iam wondering what caused the high idle rpm

                maybe carb itself leaking?
                I have ultrasonic cleaned all the parts, will redo all screws, hoses and gaskets and check again

                Whats the correct main and idle jet, is 240 and 25 okay?

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                • S
                  SpookDog @chris last edited by SpookDog

                  wow! I wouldn’t mess with the jetting until you’ve found the cause of the high revving. A split in the inlet manifold would be first try...
                  How long have you had the bike? How long has it been high revving? Have YOU altered anything?
                  P.S. Full range just means all the different sizes. I’ve seen them being sold as a set...
                  P.P.S. What is your native language?...

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                  • C
                    chris @SpookDog last edited by

                    @SpookDog
                    going to stock jets is no messing around I think
                    the inlet looks okay
                    I bought it years ago, rode it for 2 month without anything unusual and put it to a six year sleep, till now.

                    The idea of this start was to burn in the new exhaust paint, check if the cooling system that I partly redid was proof and get the motor warm for an oil change after

                    I let it run for ca 20 min till the cooling system was leaking on a hose

                    This run was with the 6+ years old crumbling airfilter, what I realised only later

                    im from ger

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                    • S
                      SpookDog @chris last edited by

                      @chris
                      Guden Tag then bud! 😎

                      Going back to standard would be bestest, but if it was running good 6 years ago I’d leave it until you work out the problem with ticking over @ 5000rpm! Even having no filter wouldn’t cause it.
                      Have you removed all the filter bits and cleaned out the carb since finding it, are you sure the slide is closing fully? No cable catching on an adjuster?
                      I usually spray a bit of carb/brake cleaner around suspected areas while the bike ticks over. If there’s a leak it usually settles down to normal revs...
                      It really does sound like a big air leak between the casing and the carb...

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                        chris @SpookDog last edited by

                        @SpookDog
                        Danke sehr

                        After that I cleaned the airbox and put a new and oiled filter in there.
                        Then I opened the carb, 5 screws were done and had to be drilled out, was a 2 hour pain in the ass work, I will use better screws with hexagon drive soon
                        I wondered how clean the carb was inside
                        The housing parts etc. are now ultrasonic cleaned and the spare parts available are ordered

                        Do the gaskets for the housing parts have to be oiled during assembly?

                        What would be the correct torque for the housing screws?

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                        • C
                          chris @SpookDog last edited by

                          @SpookDog

                          Now in hindsight I remember the choke's nut was loose
                          I didn't pay any attention to that, maybe that could be the cause of the air leak you mentioned.

                          **Do the gaskets for the housing parts have to be oiled/greased during assembly?

                          What would be the correct torque for the housing screws?**

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                          • S
                            SpookDog @chris last edited by

                            @chris
                            I’d use a small amount of grease myself. The bolts I do by instinct. You’d need a mikuni manual or search their site. It’d be almost unmeasurable unless you have a very delicate torque wrench...

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                              chris @SpookDog last edited by

                              @SpookDog
                              Yes, precisely because it is difficult to estimate, I always use a torque wrench on my rides to tighten if possible and the values ​​from the manufacturer are available
                              Mikuni manuals do not have this info apparently

                              I guess 5nm would be max for the m4 screws, and about 3nm for the brass stuff, but official data would be nicer

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                                SpookDog @chris last edited by

                                @chris
                                As long as the threads are all clean, I do them all finger tight, then 1/4 to 1/2 turn. As long as they are all the same. That’s what’s important...

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                                • Calum
                                  Calum last edited by

                                  Yeah torque wrenches have their uses, but with soft metals you have to be really careful, much better to do it by feel. It's not something that undergoes massss of stress so torquing it isn't absolutely necessary.

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                                  • C
                                    chris last edited by

                                    I found new informations, here are the essential tightening torques:
                                    Float chamber screws: 2.0 Nm
                                    Main jet: 2.0 Nm
                                    Slide cover screws: 2.0Nm
                                    Screw slide lever: 3.5Nm
                                    Drain screw: 2.0Nm

                                    carb housing gasket at https://www.gasketguru.co.uk/

                                    Also i found the throttle-spring at http://www.motocarb.com/tm-parts.html

                                    still looking for the nozzle assembly

                                    @Calum

                                    can you allow to edit posts, then I could reformat opening post and edit this infos? could be nice for others also looking for parts and stuff

                                    Calum 1 Reply Last reply Reply Quote 1
                                    • Calum
                                      Calum @chris last edited by

                                      @chris Create a new thread with the appropriate title and formatting, and I will sticky the post for you bud!

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                                      • C
                                        chris @Calum last edited by

                                        @Calum
                                        okay, will do that later when the carb is complete

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