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Problem under full throttle.

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by wgn355, Jul 22, 2009.

  1. Okay i have had my bike for nearly 2 weeks now and i've noticed that when the bike is under full throttle it dies in the arse but if u lift the throttle a bit it picks up and goes again. As i know very little bout bikes is there any reason for this. only thing i can think of is its flooding maybe?


     
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  2. Might help if you post make/model/year, how many kms etc etc.
     
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  3. Sounds like too low a float level but for sure we need to know what bike.
     
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  4. sorry its a kawasaki gpz250r 86 model(dont laugh). 97000k's
     
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  5. What do you mean "dies in the arse"?

    Does it cut out? Does it stop accelerating?
     
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  6. More like starvation than flooding.
    Does it do it straight away or after a few seconds?
     
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  7. when the bike is cold or warm? althou they warm up pretty fast
     
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  8. It stops accelerating and deosnt matter if its hot or cold. As soon as u hit full throttle u get nufin. back of a touch and away it goes.
     
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  9. Fuel pump maybe? just a guess
     
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  10. It could just be your main jet is too rich. When the needle pulls out the flow is too high. 1/4 turn back of the throttle leans it back out again.
     
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  11. If it was a single cyl, I'd say it was a blocked main jet but this is a twin..... (thinking).....has any work been done to the bike lately?

    * Too low a float level will cause it to die at full throttle after maybe 1 k of full throttle operation.

    * A rag caught in the airbox intake restricting the amount of air that can get in, can cause too rich mixture at full throttle. Many times I've see a spare rag stuffed under the seat make its way to the airbox intake.
     
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  12. needle valve not seating correctly or blocked, needle worn ?
     
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  13. would happen at the bottom not the top if it were the float needle.

    Unlikley to be worn slide needle as that's more likely to be mid-range.
     
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  14. the (insert actual correct name) needle valve on my 800 was too small and caused the carbys to run dry at too much WOT. this looks like it could be something different however if that valve was blocked or the oring not sealing correctly it could cause simmilar effects although more likely at highway cruising.

    i suck at remembering what the thingamajiggies are called
     
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  15. Doesn't have a fuel pump...gravity fed.

    Check settings related to carbs..

    float heights
    idle mixtures
    needle/seat wear
    worn/damaged slides / rubber diaphrams
    vacumn leaks ( check the fuel tap hoses - vacumn operated )
    Check fuel filter ( remove fuel tap from tank )

    Workshop manual in pdf is a pm away
     
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  16. Good call Ben...... speaking from experience lol
     
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  17. That is a really badly designed carbie that can't get enough fuel through the float needle hole at any point. It should flow about twice what the bike needs.

    It's not normally a tunable item.

    did you fix it yourself or a mechanic? If the later, he is telling porkies, or you're getting mixed up.
     
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  18. nah did it myself. my mechanic was myslef, johnny0 with a bit of help from some smart people on NR. swapped them out with some bigger ones JO had lying around and it was fixed.

    the key was, the bike originally had a fuel pump, which had been dumped for gravity fed and it just wasnt getting enough in there

    the size difference was like 1.x to 2.5 from memory.

    whether that was ever the correct size for the bike or some numpty tuner just whacked it in there i dont know
     
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  19. Now that makes more sense. I doubt the OP has the same problem however.
     
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  20. Mate if u could pm the manual would b great as i didnt get one with the bike.

    yes it has a had a bit of work over the last 2months. I'll lists what its had done as it mite help.

    The 29/5/09 it had the cam chain, clutch cover gasket, oil filter, air filter, fuel filter spark plugs changed water pipe to head and o ring for water pipe changed. As well as a new battery, tappets reset all gaskets replaced and a new heli coil to sump. Start run and tuned.

    Then again on the 12/06/09 it had new plugs a toggle switch(for the thermofan)fitted. Also valve clearance check, cam timing check, compression pressures check, carbies drained and tuned again.

    Hope it helps.
     
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