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Race bike problems - ideas?

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  • Race bike problems - ideas?

    I have a gsxr-600 k4 race bike..

    I was comin round turn 7 at a racecraft day (after a few good sessions) and revs suddenly dropped to around 10k rpm and bike sounded like it was 'missing'..

    I just changed the plugs and started her up - still won't rev past 10krpm and sounds dodgy

    Any ideas what else it could be? Just want to make sure i check everything I possibly can before forking out $ for a mechanic

  • #2
    lots of things it could be, try a compression test, may have dropped a valve

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    • #3
      make sure all of your electrics are mounted/grounded properly.

      I had a problem with an old kx80 that would stall on left hand corners. Turned out the bracket holding on the ecu (or some other electrical component), had broken, which also doubled as the ground for that unit.
      Turning left it would swing out away from the frame and bam, no spark.
      No amount of genius can overcome a preoccupation to detail.



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      • #4
        Try flushing the fuel out of the tank and trying new stuff - might only be fuel (hopefully)
        Increasing my carbon footprint - one 500 @ a time...

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        • #5
          sounds strange because that bike hasn't missed a beat all year. Did you by chance downshift and have it valve float? Might pay to do a compression check if this is the case. you may have bent a valve.
          Atlas Performance, dyna pumps, " your name goes here"

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          • #6
            when it 'went' it was under hard accelleration out of turn 7...

            Hmm being not much of a mechanic i guess it's time I call one

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            • #7
              Lubi had a similar problem with his bike on the same day I think. Found out that he had a buggered coil after some testing.

              Can you isolate which cylinder (assuming one isn't working) it was from the old spark plugs? You can test this a few different ways. turning the bike over with the spark plug in the coil and checking the strength of spark, looking at the colour/condition of the spark plug itself. Once it was isolated, he borrowed a friends bike that was working, Borrowed a coil, and used it in the cylinder that wasn't firing. Gave him good spark, and told him it was the coil that was the problem.....

              Ended up costing him replacement spark plugs (First step), some time and borrowing a bike (Second step), and buying a replacement coil (third step)
              Sponsored by:

              Billetta Imports, Motorcycle Panel & Paint, Pirelli, YAMALUBE

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              • #8
                hmm i could try that. time to pull it apart again. the old plugs all looked very similar ie no one obviously bad plug...

                ill wack them in the coils and turn it over a few times see if i can notice anything.

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                • #9
                  It was mainly a slightly different shade on the plug. The problem you might have though is you've possably got no idea which plug came from which cylinder.....
                  Sponsored by:

                  Billetta Imports, Motorcycle Panel & Paint, Pirelli, YAMALUBE

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                  • #10
                    you can use an infra red temperature sensor and check the exhaust temps on the header pipes while its running. Any difference will telltale a problem with that cylinder. I have 1 if you can't put your hands on 1.
                    Atlas Performance, dyna pumps, " your name goes here"

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                    • #11
                      I was thinking coilpacks or igniters.

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                      • #12
                        ok getting a good spark on all 4 coils with the old plugs.

                        and yes i kept the plugs in a specific order and they're all indistinguishable

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                        • #13
                          Go get a compression gauge.

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                          • #14
                            First thing i'd check would be the airbox - if something is stuck in there blocking off some of your filter? (placcy bag in it, part of it has collapsed, etc, etc)

                            Long shot, but sillier things have happened...
                            “Crashing is shit for you, shit for the bike, shit for the mechanics and shit for the set-up,” Checa told me a while back. “It’s a signal that you are heading in the wrong direction. You want to win but crashing is the opposite. It’s like being in France when you want to go to England and when you crash you go to Spain. That way you’ll never get to England!” -- Carlos Checa

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                            • #15
                              The airbox has been taken apart to get to the spark plugs - so it's been checked.

                              Will go get a compression guage this arvo.

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