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Won't go past 8,000 rpm

Discussion in 'Yamaha 250cc In-Line 4's' started by METOO, Dec 14, 2010.

  1. METOO

    METOO New Member

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    hello again...

    Well i put my bike back together with some second hand parts, insta-gasket and paint from supercheap (except for fairings) and well my excitement for my first ride again was cut short...

    The bike will not go past 8,000 with me on it and in neutral it will hit 14,000 then drop back down.

    When riding the power feels fine then at 8,000 it just hits a roadblock and stutters and struggles in every gear.

    The EXUP still does its little cycle before i start it so I'd assume thats still working.. Am i looking at carb problems here because i know the emulsion tubes and needles were pretty much gone before i crashed or could i be lucky and maybe it just needs to be re-tuned or something simple???

    It never ends with this bike.
    Thanks guys
     
  2. dontz125

    dontz125 Active Member

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    The EXUP servo cycles - good thing. Is it attached to the valve? It's not unheard of for a cable to seize / snap / go for coffee, and it sure sounds like it's stuck in the Low position.

    Pull the lower fairing on the left side (if you've installed it yet!); remove the EXUP cover on the exhaust collector (3 little allen screws). Turn the ignition and kill switch on, and watch the show. Does it go through about 60deg of arc? Does it end with the 'fork' over a little hole in the valve housing (that's your adjustment index - the fork over the hole at "start").
     
  3. Trev084

    Trev084 Active Member

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    Have a look at your electrical connections, probably upset one in the crash.
     
  4. dave

    dave Well-Known Member

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    Another thing to check - measure battery voltage while you rev it up, should stay constant over 14 volts at high rpm.
     
  5. SOBIL

    SOBIL Active Member

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    A loose air box will show the same symptoms...
     
  6. METOO

    METOO New Member

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    Sorry i haven't posted in a while. (In Malaysia... drove past sepang whoop whoop).

    Sobil was on the money, realised as i was staring at the fuel pump, trying to figure out how i could make it look better (was hanging on by cable ties haha) that the air box was not connected. So it would have came off during the crash.

    Took it down the road to get them to chuck it back on and make a bracket for the fuel pump. Went for a ride after it was put back on and the bike was not playing dice. Still did the same thing so before I left overseas I put it into a mechanic and stopped in too see him just before leaving, he said that the hoses connecting to the airbox were perished and sucking air.

    Will be back in Australia soon so hopefully it will be all sweet by the time i get back but as far as i know right now the problem was the hoses between the carbs and air box: A) not being connected and B) being cracked and perished.

    Will post when i can confirm that. Thanks for the suggestions guys
     
  7. SOBIL

    SOBIL Active Member

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    thanxs for the reply, good to know your all sorted.

    for others with the same issue you can try put a balled up sock(or a rag, i just always seem to have odd socks lying around) on top of the airbox before you but the tank down. The extra pressure keeps the air box pushed tight against the carbs
     
  8. Resist

    Resist New Member

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    This is exactly what's going on with my bike! Did you confirm that was the issue?
     
  9. METOO

    METOO New Member

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    Didn't realize I never finished this... Yeah it was the airbox causing all the problems, when I got back I'm pretty sure they put some sort of rubber sealant or something around it to make it seal and I had My bike back <!-- s:) --><img src="{SMILIES_PATH}/icon_smile.gif" alt=":)" title="Smile" /><!-- s:) -->. Oh and turns out you are supposed to have a chain guard... I didn't know that and never had one on the whole time I had my fizzer (about 2 years) no one ever told me, including the people who checked it at qld transport and the people who did the roadworthy haha (know this is unrelated but figured I'd mention it)
     

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