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Help 3LN1 Float heights

Discussion in 'Yamaha 250cc In-Line 4's' started by Forky, Jun 8, 2018.

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  1. Forky

    Forky Active Member

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    3ln carbs.... Any idea what the float level should be when measuring from the carb to the top of the float. Fully compressed it measures like 9mm and fully out measures 19mm..

    There’s too many numbers out there to know which one it is. Sick of pulling it in and out to get it to run properly. Thanks




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    Forky, Jun 8, 2018
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  2. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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  3. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    3LN1 carb specs.png
     
    GreyImport, Jun 8, 2018
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  4. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Float height is 16mm with the tab just touching the tip of the needle
     
    my67xr, Jun 8, 2018
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  5. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Guys check me on this but isn't a 1990 Fizzer more likely a 3LN3?

    @Forky - certain it's a 3LN1?
    Different float heights/fuel levels between 3LN1 & 3LN3

    or tell me to rack off because I've got it wrong :p
     
    ruckusman, Jun 8, 2018
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  6. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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  7. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    How should I rack off O'Grand Poobah? :p :p :p
     
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  8. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    I hadnt heard that saying for ages ... u must be in the vintage class like me :cool:
     
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  9. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    He has checked it's a 3LN1
     
    my67xr, Jun 8, 2018
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  10. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Yeah I'm getting up there, but seem to have a good memory for some sayings - even managed to recite the "big mac" ingredient list, which from when I was about 10 years old if you could do it in less than 20 seconds you got something cheaper or free
     
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  11. Forky

    Forky Active Member

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    I’ve adjusted to spec including mixture, and still has dramas starting. But once it goes it sounds okay. But won’t idle for too long.

    It seems as though when I pull carbs off and drain the fuel in the floats and reinstall it, and prime the pump, it try’s to start by itself. But when it idles, say a minute, it dies..

    Thoughts?


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    Forky, Jun 8, 2018
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  12. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Sound's like the fuel level/s may be a touch high to me ?
    Or there's a blockage in the pilot circuit somewhere

    Have you double checked the fuel level in each fuel bowl using the clear hose method ?
    The fuel level should be 9.2mm above the line on the outside of the float bowl
     
    my67xr, Jun 8, 2018
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  13. Forky

    Forky Active Member

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    I’ll have to try this method to be absolutely sure. Are you able to produce a pic as to where I put the hose and so forth?


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  14. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Read the litetek link posted above
     
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  15. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    ruckusman, Jun 8, 2018
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  16. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Yes, your good work is on my web page which is the first response to this question.
     
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  17. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    maelstrom, Jun 8, 2018
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  18. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    I noticed, however he's also asked about which screws and where to plumb the tube to check the fuel height...he likely benefits from both as yours had a good explanation of which lines to measure from ;)
     
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    ruckusman, Jun 8, 2018
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  19. Forky

    Forky Active Member

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    I’ve set the floats to 16mm and 2 twists out for mixture. I’ve have just done the clear hose method and all Checks out to 9mm above the central line on the float case. And still nothing


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    Forky, Jun 9, 2018
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  20. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Trying to correctly diagnose a fault with a motorcycle, particularly one that is 30 years old with an unknown history, is difficult. Trying to do the same with text messages is far more difficult. Then when those messages don't tell you much, like "And still nothing" becomes pointless. If you would like the members here to help you then you must be very, very specific in your description.
     
    maelstrom, Jun 9, 2018
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