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Project First bike, the FZR250 3LN

Discussion in 'Your 250cc Projects' started by I_b_pirate, Feb 17, 2020.

  1. I_b_pirate

    I_b_pirate Member

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    Yeah im gonna go through motorcycle spares, they have the 3ln1 kits and i just trust going though a reputable company rather than some guy on eBay. Over the weekend ill check the spark plugs. They are new but I wanna see the state they are in after a few spins. It was running but not great down low. I did forget to turn the fuel off after the last trip and the tank was dry when i went to start it the next day so I might leave the plugs out overnight to dry out the cylinders.

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  2. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    All that fuel has probably made its way into the sump, you should replace the oil and filter. The fact it leaked out tells that the needle valves are not sealing.
     
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  3. I_b_pirate

    I_b_pirate Member

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    Yeah thats what I was thinking too. Ill wait till the kits arrive before I start striping down the carbs and ill pick up a new filter this week.

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  4. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    look for a leaking fuel tap ... common
    as mentioned ... float needles shot ... common

    take off the carbys and look for fuel in the cylinders as below
    and as mentioned , if its leaked thru the oil will be contaminated

    If its happened, leave the carbys off , plugs out and oil out with the filler and sump plug out , for a day or 3 to let the fuel evaporate
    If theres fuel sitting in the cylinders , with the plugs out, put it in gear and roll it forward a little to expel it



    float needles available from motorcycle spares warehouse also

    https://www.motorcyclespareswarehouse.com.au/products/kvn-16qs2?_pos=13&_sid=fb506670e&_ss=r

    fuel in cylinder.JPG
     
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  5. I_b_pirate

    I_b_pirate Member

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    So re built the carbs and it struggles to idle even with the choke plus it won't go over 6k and it pops and backfires another pretty sure I have to adjust the pilot screws. Also not sure where the exup cables go. I have number 1 on the servo going to the top of the valve atm

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  6. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Sound's like float height's are wrong?
    And how many turn's out are your mixture screw's seat at ?
     
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  7. I_b_pirate

    I_b_pirate Member

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    Screw are set to 2.75 turns out and i didnt change the floats from before, would changing the float needles change the heights?

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  8. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Quite possible if the needle valve springs are worn, new ones would potentially raise the float height
     
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  9. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    EXUP valve should rotate when you turn on the key - so that is easily checked for functionality just visually

    BTW if the EXUP isn't working, it won't rev

    Long thread now an I'm feeling lazy, have you been through checking the fuel level, you can check it with the carbs on the bike

    OK, so I've checked, you've done valve clearances, rebuilt carbs - need to re-check that fuel level to know if you may or may not need to adjust the float height given that the needles/seat valves are new as @Linkin has suggested
     
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  10. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Yeah the new float needle's might be making the float's sit further away from the carb body (Higher float levels, Lower fuel height's), this will make it a bit leaner and wont want to rev
    The Keyster one's are stronger than the oem

     
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    Last edited: Aug 31, 2020
  11. I_b_pirate

    I_b_pirate Member

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    Ok so just checked the float levels and they all look good at about 9mm above the cast line. I had the main needles set at the top notch cause thats what the old ones were at so took them all down a notch but too late to start now so will try it tomorrow

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  12. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Standard setting is the middle notch, likely someone has tried to lean it off as a bandaid to cover worn out needles/tubes.
     
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  13. driftwood

    driftwood Member

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    Mine had flooding enuff to call in the SES, due to a shabby O-ring on float base. p/n 3en-14147 nil stock Oz, going to local specialists tomorrow.
     
  14. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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  15. driftwood

    driftwood Member

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    Impatient to get away, so went for a local supplier of BS011 NBR70 rings.
    Firm press fit, petrol rated. 50c EA.
     
  16. driftwood

    driftwood Member

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    It seems that spring strength is pivotal in where the float sits when measured - but what matters is float height when valve seats home.
     
  17. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Float height is meant to be set with the float just touching the needle valve, but not compressing the spring. So if the spring is worn or sticky, it can affect the measurement. A new needle valve with a good spring will let the float rest on it without compressing too much or at all.
     
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  18. I_b_pirate

    I_b_pirate Member

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    When i get her running she runs on 3 cylinders im thinking I did something wrong with the carb. Wont start with the choke at all but when it's warm it can and i put the choke on slowly the missing cylinder fires up so im thinking a jet must be blocked somehow. Really refuses to start when it's cold but will start after some persistence.

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  19. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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  20. I_b_pirate

    I_b_pirate Member

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    Remembered one of the jets were seized in but it wasn't a problem before so I just left it. Turns out it was the problem now. Managed to get it with an easy-out and she fires on all 4 but still a bit rough. The only thing that wasn't replaced on the carbs was the diaphragms. They felt fine but as a process of elimination I think ill replace them. Where's a good cheap but quickly delivered place i can get them for the 3ln1?

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