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Help Nightmare FZR carbs/fuel system

Discussion in 'Yamaha 250cc In-Line 4's' started by logan anderson, Nov 3, 2017.

  1. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Just noticed your fuel line is only 4.7mm (3/16) should be 6.5mm minimum
     
  2. logan anderson

    logan anderson Active Member

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    Would that be 6.5mm all the way though?
     
  3. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Yeah mine has the original fuel line still there and ok, i reckon that's at least 7mm i/d

    This top airbox boot look's like it is covering the pilot air jet a little, and could affect the mixture's

    [​IMG]
     
  4. logan anderson

    logan anderson Active Member

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    looks like it's not sitting correctly, I wonder if that's from when I pulled it off in the past and did not install it correctly. Either way, I'd be happy to get any spooge out of the fuel system asap
     
  5. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    The air box boot's do look pretty new, and they can shrink after a few year's so i wouldn't worry too much about them being glued to the air box
     
  6. logan anderson

    logan anderson Active Member

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    Sometimes I should listen to myself :p
    Pulled the carbs last night, the manifold boots are pretty solid, does not look like there are any cracks that go all the way though, however since I have them I may as well replace them.

    Turns out the carbs are pretty clean so far (after removing the glue)
    Except some discoloration in the steel of the float bowls they are cleaner than I expected

    WLScSI5.jpg

    Under the floats themselves there is some granulated rust and the seal surfaces need to be cleaned. However I'll still do the needles since I've brought them and probably are 28 years old
    eFOls4Y.jpg
    QMUz86D.jpg

    So far I've pulled the float bowls off, seperated all the carbs and ground a screw head off (don't ask)
    The T piece was not broken (it kinda looks shorter than it's meant to be so may be from something else), however the little seal bits on there ends ended up ripping getting the glue off, so luckily I have that coming.

    Just have to wait on parts now.....
     
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  7. logan anderson

    logan anderson Active Member

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    So parts Christmas has happened (don't get me started on the courier company)
    So far all I'm waiting on is fuel line then I should be good to go.
    I've pulled one carb down and rebuilt her, disassembled one other. have not found anything too bad except for one of the butterfly plates being a complete pain to get out and a bent needle (not sure how the old needle is going to go with the new slot thingy but we'll see)

    45aXw7w.jpg

    Old filter vs new filter

    xOHFyiO.jpg

    new Fuel pump and carb boots

    oKWkwRb.jpg

    In terms of adjustment, whats the go, I can see we have the mixture and idle screws, but what about float etc
     
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  8. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    That's a beautiful picture with all those new parts :bowdown:
     
  9. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Be aware @my67xr posted recently that the keyster kits had the incorrect main jets in the corresponding carb kits - the mains for the centre two carbs were in the kits for the outer carbs and vice versa

    If you want to go by the numbers on the main jets the centre carbs have the smaller main jets because the air intake gets hotter, becoming less dense and requires less fuel
     
  10. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Why would you use and old needle with the new slot ?
    Is that the slide needle and the needle jet (emulsion tube) ?
    Set the mixture screw's to 3 turn's out, then when you start the bike and warm it up you can tune them from there.
    Should have it at normal operating temperature before adjusting the mixture's.


    They're 3LN1 carby's aren't they ?
    The main jet's in the Keyster kit's for the outer carby's were right in the listing's on the box's i'm pretty sure.
    Did you double check the numbers on the main jet and other jet's from that carby to make sure it was all the same?

    Float height for the 3LN1 carb's should be 16mm off the fuel bowl mounting face on the carby, with the tip of the needle just touching the adjusting tab on the float
    There's a pic on the Litetek site
     
  11. logan anderson

    logan anderson Active Member

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    Yeah the float hight was a bit of head scracher as it took a while to figure out what it meant.

    I used the old needle as I installed the new one incorrectly and bent it, not my proudest moment but it does not looke like they are too worn. I might grab the tube and needle out of the other one in case I run into problems

    Didnt think to check the jet numbers
     
  12. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    The needle's are a different shape in the Keyster kit's (thinner in the 3LN3 kit's), so i think they are to suit the Keyster emulsion tube's only, 3LN1 may be different ?
     
  13. logan anderson

    logan anderson Active Member

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    Ah ok, will that make a big impact if I have 3 keyster and 1 orginal?

    I checked the boxes, they say they are bigger on the outside ones so I'll check them tomorrow and see whats printed on the jets, though the orginals have no numbers
     
  14. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Yeah might pay to check the Keyster and original needle's against each other when you rebuild the other outer carby
     
  15. beano

    beano Well-Known Member Premium Member

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    pretty sure the 3ln-1 carbs are set to two turns out on the mixture screws, the outer carbs main jets should be 102.5 and inners should be 100. Do everything else as per Craigs advice above, particularly the float heights, i personally found this to be the single biggest impediment to smooth running. best of luck.
     
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  16. logan anderson

    logan anderson Active Member

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    Yeah no numbers on those jets. Look around the same size.

    Hopefully should have her started today
     
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  17. logan anderson

    logan anderson Active Member

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    So got them togeather, synced them by eye (nothing to use as a feeler gauge) and attched them to the bike. Turned it over and got nothing for a few secounds untill fuell started gushing out of the float breather on one side and the too of the carb; turns out I absolutly screwed uo the float hight. After a remeasure and adjustment she started, screwed the mixture screw in half a turn then either in or out a quarter turn and she ran sweet off of the gas can.

    Think im still going to find bigger fuel line from the peacock to the tap cause after outting the tank back on she runs a little rough (though like an idiot I set the exup AFTER tuning the carbs)

    Hopefully be able to take her for a ride next few weekends and see how she handles actual riding
     
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  18. logan anderson

    logan anderson Active Member

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    My question is, does anyone have the skill or knowledge to make a remote float adjustment setup so you could mount them in a easier to reach place?
     
  19. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    You could put a bench next to your bike to sit the carby's on, and run a fuel line from you bike to the carb's.
    Have the carb's sitting at the same angle as they would on your manifold's and check them like that
    I made a makeshift stand to set my float height's but haven't used it yet, at least i get some use out of my old cracked manifold's, lol
    I can turn the screw's in the underside of the wood in or out to adjust the angle the carb's sit at

    20171115_170348.jpg 20171115_170359.jpg
     
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  20. logan anderson

    logan anderson Active Member

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    Im hoping the card trick has worked
    Im getting a tiny bit of smoke out of the tail pipe, couls that be related to tuneing?
     

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