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bike becomes sluggish after five minutes of riding

Discussion in 'Yamaha 250cc In-Line 4's' started by dohctor, Oct 9, 2009.

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  1. dohctor

    dohctor New Member

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    ive noticed that my fzr starts to become sluggish after a short period of riding, usually what happens is that it will loose almost all throttle response and just put along the road, however the next day it rides normal. Today is started to become flat and i noticed that if i let off full throttle a bit the bike would start riding normal however applying the slightest amount of more throttle would take me back to square one. this eventually became a matter of me limping the bike back home im just curious to know why this is happening.

    has oil, petrol, coolant however dont know about tuning (just bought it, well not really but havent really ridden it as its a project)
     
    dohctor, Oct 9, 2009
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  2. dave

    dave Well-Known Member

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    At a guess I would check that you are getting a full flow of fuel to the carbs. It sounds like the you may be starving of fuel once the float bowl level drops with heavy usage and there is not enough supply to keep them full.

    Hoses can block, as can the fuel tap,filter (if you have one) or the fuel pump may mot be pumping.
     
    dave, Oct 10, 2009
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  3. dohctor

    dohctor New Member

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    that may be something i over looked, ill try running it on reserve, i might pull the whole thing apart today and tune the carbys. im more experienced with cars however i want to learn more about bikes. after reading that tutorial it seems that the carbys arent too hard to tune. just to confirm, its basically a matter of adjusting all the butterfly valves in sequence so they all open at the exact same time is this correct?
     
    dohctor, Oct 10, 2009
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  4. dave

    dave Well-Known Member

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    What you are referring to is a carb balance where the vacuum of all the carbs are equalised. Normally this is all that is required.
     
    dave, Oct 10, 2009
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  5. dohctor

    dohctor New Member

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    do the carbs 'lose their balance" over time?

    i guess that is about it, ill have a better look at it i guess and see how i go. i hope this isnt why i bought it so cheap
     
    dohctor, Oct 10, 2009
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  6. Romantix1

    Romantix1 New Member

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    ahh, u know the FZR250 is a high revving bike right?
     
    Romantix1, Oct 12, 2009
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  7. dohctor

    dohctor New Member

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    i dont know what that was in reference to, carbs or the sluggish problem, if you think i may be misinterpreting the time it takes to "get going", the answer is no. its more of a loss of power in which full throttle does nothing but keep it from stalling.
     
    dohctor, Oct 12, 2009
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  8. dave

    dave Well-Known Member

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    This seems to be a problem that some 3LNs aquire.. My only suggestion that it is a combination of carby and perhaps valve (and even exhaust) related problems, where the opening of the throttle does not cause the airflow into the engine to increase. I have not heard of 2KRs doing it. The carbs are different on 3LNs.

    Recommend a valve clearance check and a thorough carb check, and perhaps an EXUP alignment
    check...
     
    dave, Oct 12, 2009
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  9. dohctor

    dohctor New Member

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    ive been meaning to check the carbys, im guessing there is a tutorial on valve clearance and exup adjustment?

    One more quesiton, is it ok to just clamp the fuel line when taking the tank off the body to get to the carbys?
     
    dohctor, Oct 13, 2009
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  10. dave

    dave Well-Known Member

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    There is reasonable descriptions in the "how to" section

    It would probably work but I would not recommend it, sounds like your stop tap does not work. Just have a backup plan in case of petrol leaks occurring.
     
    dave, Oct 13, 2009
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  11. Romantix1

    Romantix1 New Member

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    wtf there is a stop tap? lol, wow, probably would have been a funny sight seeing me cleanup my carb rofl.

    Ended up pullin hose off and tipping tank upside down XD

    worked just as well as a stop tap, no fuel came out xD
     
    Romantix1, Oct 13, 2009
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  12. hagenstew

    hagenstew New Member

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    Don't leave your tank upside down for too long. It will perish the rubber seals on top that the filling cap sits on.

    Speaking from experience here... Repainting my freshly painted tank because all the paint all bubbled up was not my idea of a good time.
     
    hagenstew, Oct 14, 2009
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  13. dohctor

    dohctor New Member

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    Ohk what is this stop tank were speaking about?
    If your referring to the dial on the lhs for switching to reserve etc i didnt think that would make a difference as the fuel runs from the tank via lines down into the engine compartment, i want to know how to take off the tank without fuel pouring out of the it.
     
    dohctor, Oct 14, 2009
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  14. METOO

    METOO New Member

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    [quote="dohctor" i want to know how to take off the tank without fuel pouring out of the it.[/quote]
    simple.... empty it <!-- s:) --><img src="{SMILIES_PATH}/icon_smile.gif" alt=":)" title="Smile" /><!-- s:) -->
     
    METOO, Oct 14, 2009
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  15. dave

    dave Well-Known Member

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    You should be able to find "on" "res" and "off" on that fuel tap.. "On" is the normal running position, "off" is the no fuel position. Might not be marked exactly as that though..
     
    dave, Oct 14, 2009
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  16. dohctor

    dohctor New Member

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    yeah i know exactly what your talking about, but when i un bolted the fuel tank i noticed all that was left was some fuel lines running from the bike to the tank itself, now being that the tap is located on the lower section of the fuel line i am concerned that switching it off will only block access to fuel which is going into the bike but still allowing fuel to freely flow from the tank. How to i pull the fuel lines out of the tank end without fuel pissing out everywhere?

    do you get me? maybe im just not seeing the point so sorry on that one.
     
    dohctor, Oct 15, 2009
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  17. dave

    dave Well-Known Member

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    Ahh - It looks like the 3LN fuel valve is not mounted on the tank. The 2KR has the valve mounted in the tank, and so is not an issue. I only had a 2KR model and was unaware of the difference <!-- s:oops: --><img src="{SMILIES_PATH}/icon_redface.gif" alt=":oops:" title="Embarassed" /><!-- s:oops: --> ..
     
    dave, Oct 15, 2009
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  18. dohctor

    dohctor New Member

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    Oh thats cool, however im still stuck lol. Can i just clamp the hose or something? what do you suggest.
     
    dohctor, Oct 16, 2009
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  19. dave

    dave Well-Known Member

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    I would guess best option - clamp it off and drain into a jerry can once you get the tank off.
     
    dave, Oct 16, 2009
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  20. maxfacta

    maxfacta New Member

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    Leave the fuel lines attached to the tank, unbolt the tap from the frame and remove them together. (Obviously remove the outgoing line from the fuel tap.)
     
    maxfacta, Oct 20, 2009
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