/ Register

  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Help Nightmare FZR carbs/fuel system

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

Page 3 of 4
  1. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

    Messages:
    4,313
    Likes Received:
    2,383
    Trophy Points:
    898
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide, South Australia
    My Bike:
    Yamaha's , 1990 FZR250R 3LN3 , 1986 XT250TS 57R , 1984 IT200L 43G, 1976 IT400C 510
    Black smoke ?
    Might be a touch rich ?
    How many turn's out are you mixture screw's?
    And where they set with the engine at operating temperature ?
     
    my67xr, Nov 15, 2017
    #41
  2. logan anderson

    logan anderson Active Member

    Messages:
    75
    Likes Received:
    18
    Trophy Points:
    178
    Joined:
    Apr 9, 2017
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    Yamaha FZR250r 3ln1
    It was warm not sure about hot. Its either 2.25 or 2.75 turns out

    Is it in to make it leaner and out to make it richer?
     
    logan anderson, Nov 15, 2017
    #42
  3. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

    Messages:
    4,734
    Likes Received:
    2,874
    Trophy Points:
    943
    Joined:
    Mar 18, 2014
    Location:
    Sydney NSW
    My Bike:
    FZR250R 3LN6
    That is correct as the screws control the amount of fuel. Fully seated - no fuel flow and it would only run on choke.

    As you wind the screw out, the fuel flow is increased.

    3 turns is standard, but that amount of fuel flow is for the standard exhaust system. If the end can has been gutted or replaced, you would need to lean it out as higher exhaust flow = more hydrocarbons escape during valve overlap.

    Also an important note - as your valve clearance decreases, your valves are open for slightly longer periods of time, so more hydrocarbons will escape during overlap
     
    Linkin, Nov 15, 2017
    #43
  4. logan anderson

    logan anderson Active Member

    Messages:
    75
    Likes Received:
    18
    Trophy Points:
    178
    Joined:
    Apr 9, 2017
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    Yamaha FZR250r 3ln1
    Yeah valve clearances will be the next big job after shes running right
     
    logan anderson, Nov 15, 2017
    #44
  5. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,230
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    ruckusman, Nov 16, 2017
    #45
  6. Gert

    Gert Well-Known Member

    Messages:
    124
    Likes Received:
    122
    Trophy Points:
    248
    Joined:
    Jun 14, 2016
    Gender:
    Male
    Location:
    The Netherlands
    Personally, I found that adjusting fuel level was not easy. The only way I could manage an good level was to remove, check and test, remove, check and test, etc, etc, and that a dozen times.
    In the end, the bike runs ok with the Keyster tube, needle and float valve. Cold start is an disaster though.
    https://www.2fiftycc.com/index.php?threads/fzr250-3ln3-carb-problem.8770/page-3#post-90908

    I see how things go, but perhaps I will try to get me original parts, dunno. I have sleep about it.
     
    Gert, Nov 16, 2017
    #46
  7. logan anderson

    logan anderson Active Member

    Messages:
    75
    Likes Received:
    18
    Trophy Points:
    178
    Joined:
    Apr 9, 2017
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    Yamaha FZR250r 3ln1
    Well first ride tonight, lots of hesitation and a nightmare to get above 4 grand so I think Im gonna be playing with the carbs for awhile, sadly we have a house inspection soon so going to be a week before I can do anything to it
     
    logan anderson, Nov 16, 2017
    #47
  8. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

    Messages:
    4,313
    Likes Received:
    2,383
    Trophy Points:
    898
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide, South Australia
    My Bike:
    Yamaha's , 1990 FZR250R 3LN3 , 1986 XT250TS 57R , 1984 IT200L 43G, 1976 IT400C 510
    Try the mixture screw's out half a turn from where they are now to correct the hesitation. Might need to raise the float levels a touch too, try them at 15.5mm or 15mm to fix the 4000rpm and up problem
     
    my67xr, Nov 16, 2017
    #48
  9. logan anderson

    logan anderson Active Member

    Messages:
    75
    Likes Received:
    18
    Trophy Points:
    178
    Joined:
    Apr 9, 2017
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    Yamaha FZR250r 3ln1
    Yeah, have to drain the tank top. I have an idea of what might be but see what happens after wednesday
     
    • Like Like x 1
    logan anderson, Nov 16, 2017
    #49
  10. logan anderson

    logan anderson Active Member

    Messages:
    75
    Likes Received:
    18
    Trophy Points:
    178
    Joined:
    Apr 9, 2017
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    Yamaha FZR250r 3ln1
    SUCCESS!!!!
    Pulled the carbs off when I got home after having a poke around the fourms and the net at work. Adjusted the needle to the third setting (stock), and found out who ever didbthe carbs before me put the spacers for carbs 2 & 3 into carbs 3 & 4. Set the mixture at 2 turns: Started right up.

    Put her back togeather with bigger fuel lines (need a slightly smaller size for the tank to tap) and took her for a run. She runs nearly perfectly, is a tiny bit of hesitation between 4 and 7 k (very slight) which changes the exhaust tone a bit, but above that she pulls all the way tp redline no problem.

    Think an 1/8-1/4 turn should bring her to perfection!!!
     
    • Like Like x 1
    • Informative Informative x 1
    logan anderson, Nov 17, 2017
    #50
  11. logan anderson

    logan anderson Active Member

    Messages:
    75
    Likes Received:
    18
    Trophy Points:
    178
    Joined:
    Apr 9, 2017
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    Yamaha FZR250r 3ln1
    Out of intrest, has anyone tried emptying their float bowls as a way of checking float hight?
     
    logan anderson, Nov 17, 2017
    #51
  12. beano

    beano Well-Known Member Premium Member

    Messages:
    176
    Likes Received:
    129
    Trophy Points:
    248
    Joined:
    Jan 20, 2005
    Gender:
    Male
    Occupation:
    Mechanical Engineer
    Location:
    Ireland
    My Bike:
    FZR250r and YZF-R1
    As in measuring the volume of fluid that comes out?? I suppose its a valid way of measuring it alright, cant see why it would'nt work, but there's plenty of little nooks and crannies in the float bowl that can hold on to a few milliliters, i'd imagine it would have been done by now if it was an accurate way of doing things.
     
    • Agree Agree x 1
    beano, Nov 17, 2017
    #52
  13. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

    Messages:
    4,313
    Likes Received:
    2,383
    Trophy Points:
    898
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide, South Australia
    My Bike:
    Yamaha's , 1990 FZR250R 3LN3 , 1986 XT250TS 57R , 1984 IT200L 43G, 1976 IT400C 510
    So you have ridden it like that ?
    Or is that with it sitting still?
    Yeah you could use the measured cc's of fuel as a way to calculate what height the float's are at, would take a bit of playing around though.
    The clear hose off the fuel drain is much easier (if the carby's are off the bike), that's the way Yamaha set them up.
     
    my67xr, Nov 17, 2017
    #53
  14. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

    Messages:
    4,313
    Likes Received:
    2,383
    Trophy Points:
    898
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide, South Australia
    My Bike:
    Yamaha's , 1990 FZR250R 3LN3 , 1986 XT250TS 57R , 1984 IT200L 43G, 1976 IT400C 510
    This pic is of an FZR1000 carby, it shows where the fuel level need's to be so it doesnt hesitate off idle and through the needle/needle jet position's of the throttle
    Disregard the blue and red circle's

    On your carby's that fuel level should be 9.2mm above the line on the bowl on the outside

    bdst fzr1000.jpg
     
    my67xr, Nov 17, 2017
    #54
  15. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

    Messages:
    10,929
    Likes Received:
    6,713
    Trophy Points:
    1,168
    Joined:
    Jun 14, 2012
    Gender:
    Male
    Occupation:
    Between a Rock and a Hard Place
    Location:
    North by NW NSW Oztralia - Tamworth
    My Bike:
    *Kawasaki ZXR250C *Yamaha FZR250R 3LN1 *Yamaha FZR400 *Triumph Bonneville 750 T140V *Triumph Daytona 675 *Triumph Tiger 800XC
    Fuel level carb 1.jpg


    Fuel level carb 4.jpg
     
    • Agree Agree x 1
    GreyImport, Nov 17, 2017
    #55
  16. logan anderson

    logan anderson Active Member

    Messages:
    75
    Likes Received:
    18
    Trophy Points:
    178
    Joined:
    Apr 9, 2017
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    Yamaha FZR250r 3ln1
    Yeah, I just got the idea when I drained the float bowls last night.
    Riding it at the moment, going to try and adjust the mixture today, hopefully I don't get bombarded with too many customer requests
     
    • Nice Work Nice Work x 1
    logan anderson, Nov 18, 2017
    #56
  17. logan anderson

    logan anderson Active Member

    Messages:
    75
    Likes Received:
    18
    Trophy Points:
    178
    Joined:
    Apr 9, 2017
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    Yamaha FZR250r 3ln1
    Well won't make that mistake again, power outages in a datacentre are a nightmare. Mixtures at 2 1/4. feels the best it ever has!!!

    There's still a slight flat spot between 4 and 6 1/5 though I'm getting the feeling that it's apart of the power out put now as 2 turns is too lean and 2.5 is too rich. in saying that, maybe I didn't adjust the exup correctly

    I might order a new needle to replace the one that I bent after checking the old needles and finding all of them well worn.

    Other than that, I'm declaring the carbs conquered!!!!
     
    logan anderson, Nov 19, 2017
    #57
  18. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

    Messages:
    4,313
    Likes Received:
    2,383
    Trophy Points:
    898
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide, South Australia
    My Bike:
    Yamaha's , 1990 FZR250R 3LN3 , 1986 XT250TS 57R , 1984 IT200L 43G, 1976 IT400C 510
    Pretty sure Keyster don't sell the needle's individually for the FZR's.


    With the EXUP, try the both the cable's a half turn looser.
    If that doesn't help, you'll need to raise or lower the fuel level a touch
     
    my67xr, Nov 19, 2017
    #58
  19. logan anderson

    logan anderson Active Member

    Messages:
    75
    Likes Received:
    18
    Trophy Points:
    178
    Joined:
    Apr 9, 2017
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    Yamaha FZR250r 3ln1
    Well I sure did mess up. after a week or so riding it to work I decided to recheck the float height the proper way, pretty much every single carb was way over (10mm+ on some). went though and reset them all back to 9.2mm and set the mixture back to 2 turns, found out I had been riding with the 3rd cylinder's mixture screw all the way in for about a week after some road side tuning :s.

    But a lot more power below 6K now and a lot quicker to start :)
     
    • Like Like x 2
    • Nice Work Nice Work x 2
    logan anderson, Nov 25, 2017
    #59
  20. logan anderson

    logan anderson Active Member

    Messages:
    75
    Likes Received:
    18
    Trophy Points:
    178
    Joined:
    Apr 9, 2017
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    Yamaha FZR250r 3ln1
    So has anyone had problems with their bike not going over 100 or having really poor performance at open road speed?
     
    logan anderson, Nov 28, 2017
    #60
Page 3 of 4

Share This Page