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    The pursuit for a brown sparkplug

    Carburetor
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    • Irongamer727
      Irongamer727 last edited by

      0_1523479617203_20180411_170225.jpg 0_1523479621613_20180411_170218.jpg

      Alright, trying to set up this Athena kit. Currently running 280 main jet and this is what the sparkplug looks like after ~250km. Looks pretty good huh? Sadly, the bike won´t rev fully, no power beyond 3/4 throttle. Running lumpy, strange. Wouldn´t say bogging but something is certainly not right down there. The question is, should I go down to 270 or up to 290? What´s your opinion? Personally, I´d want to try a smaller since almost everyone with the kit runs 270. However, since I´ve not pushed the bike that much during break-in, and the sparkplug isn´t completely black from a very rich mixture, I´d say I might as well try 290. A safer bet for sure.
      And no Calum the pv is not pinned in the closed position 😉

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      • Calum
        Calum last edited by

        It's not really appropriate to be judging the fueling on break in, you need to put that engine under load and perform a plug chop to really understand how the fueling is doing.

        Once it's bedded in, perform a plug chop and report back what the plug is doing then.

        I'd say that plug looks a tad lean to me.

        Easiest way to tell is to restrict the air flow into the bike, if it performs better then you know you need to increase the fueling.

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        • J
          Jens Eskildsen last edited by

          This is mine (no kit though), a bit of deposits from excess oil, but otherwise tan as Hasselhoff!!
          0_1523556008934_plugchop.JPG

          1 Reply Last reply Reply Quote 2
          • Irongamer727
            Irongamer727 last edited by

            Wow! I'm impressed! I'm now running 290 main jet. Can't feel much difference. My issue is, it does not pull after 3/4 throttle. The revs go up, exhaust getting louder, I brace for the real powerband but then nothing.. Dropping to 3/4 and she goes! But there is definitely power left to scavenge. My next alternative is to try a 270 main jet. And yes I've tried the choke, no results.
            Should I really be giving the piston, cylinder full throttle? I'm closing in to 300km.. Shouldn't be an issue right?

            1 Reply Last reply Reply Quote 0
            • Irongamer727
              Irongamer727 last edited by

              This post is deleted!
              1 Reply Last reply Reply Quote 0
              • Irongamer727
                Irongamer727 last edited by

                I've tweaked the oil pump a bit for my Athena, will this dramatically lean the mixture? As I've said, I'm running far bigger jets than anyone I've seen used the big bore kits.

                Darty 1 Reply Last reply Reply Quote 0
                • Darty
                  Darty @Irongamer727 last edited by

                  @irongamer727 What is your bike not doing?

                  I dont get it.

                  Irongamer727 1 Reply Last reply Reply Quote 0
                  • Irongamer727
                    Irongamer727 @Darty last edited by

                    @darty it's not performing well in the upper revs. The jetting is off, I'm steadily climbing in sizes (now 320) but the plug still looks a bit too lean.

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                    • Irongamer727
                      Irongamer727 last edited by

                      And I have a friend running 240 with the kit. We are both running stock Air box and so forth.

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                      • Glynn123
                        Glynn123 last edited by

                        Are you certain there's no leaks between carburettor and crank case? No head gasket leak, and no leaks in the carburettor itself allowing air in?
                        I'd say there's definetely a leak somewhere allowing a lot of extra air in.

                        Irongamer727 1 Reply Last reply Reply Quote 0
                        • Irongamer727
                          Irongamer727 @Glynn123 last edited by

                          @glynn123 nope everything is sealing, not leaking etc.

                          1 Reply Last reply Reply Quote 0
                          • Calum
                            Calum last edited by

                            You using the stock carb? Pretty sure they use a powerjet which should be the jet you want to be changing.

                            Irongamer727 1 Reply Last reply Reply Quote 0
                            • Irongamer727
                              Irongamer727 @Calum last edited by

                              @calum yep there is a powerjet. I'll give the really big jets a try first. Because again, I've not heard anyone changing anything but the main jet.

                              Calum 1 Reply Last reply Reply Quote 0
                              • Calum
                                Calum @Irongamer727 last edited by

                                @irongamer727 So the powerjet kicks in at wide open throttle.

                                You should be doing a plug chop at WOT.

                                Therefore, changing the main jet won't affect the colour of the plug during a plug chop.

                                Irongamer727 1 Reply Last reply Reply Quote 0
                                • D
                                  DTR+NSR last edited by

                                  Pretty sure the power jet isn't changeable on these carbs.

                                  1 Reply Last reply Reply Quote 0
                                  • Irongamer727
                                    Irongamer727 @Calum last edited by

                                    @calum I'm currently going WOT sixth gear and turn ignition off. I can thereby see the plug colour at WOT. And it still looks a tad to white for my taste.

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                                    • Darty
                                      Darty last edited by Darty

                                      The Powerjet is a fixed system on the TM28,

                                      I used to run 340 Main, 30 Pilot, only because of extensivly modifing the Airbox volume,

                                      And, it was rubbish mostly.

                                      I had to replace my main body Carburettor gaskets because of symptoms near enough the same as you.

                                      I would recomend throughly checking for Air leaks as this is almost certainly your problem!

                                      Dont just throw fuel at this and hope for results.

                                      Work backwards.

                                      Irongamer727 1 Reply Last reply Reply Quote 1
                                      • Irongamer727
                                        Irongamer727 @Darty last edited by

                                        @darty how would you check for Air leaks then?

                                        1 Reply Last reply Reply Quote 0
                                        • Irongamer727
                                          Irongamer727 last edited by

                                          I do have the entire pice where the snorkel existed cut out. So there that as well.

                                          Darty 1 Reply Last reply Reply Quote 0
                                          • Darty
                                            Darty @Irongamer727 last edited by Darty

                                            @irongamer727 You donkey,

                                            Why dont you try and restrict Air by patching up a section of the Airbox,

                                            By doing so, i’ll bet a Roast dinner that it sorts out your lean condition.

                                            I’ve played around alot with this, you’ll stuggle to fuel this properly with the TM28

                                            Irongamer727 1 Reply Last reply Reply Quote 1
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