/ Register

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

Help 3LN1 Float heights

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

Page 2 of 3
  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
    Are you using full choke?
    Might be worth trying it with the mixture screw's turned further out, go 1/4 turn at a time and try again.
     
    my67xr, Jun 9, 2018
    #21
  2. Forky

    Forky Active Member

    Messages:
    45
    Likes Received:
    17
    Trophy Points:
    78
    Joined:
    Apr 13, 2018
    Gender:
    Male
    Location:
    Brisbane
    My Bike:
    1990 Yamaha FZR250r
    Still nothing refers to “not starting by itself”. It’ll struggle to start, but starts nonetheless when you tip a little petrol down the carbs.

    The revs are high at around 4K when it starts then drops to idle after about 15-25 seconds. I’ve tried half turns, quarter turns and the revs will change, So I try adjust to what I believe it’s a nice idle then turn off to see if it will start by itself. Then it’s goes back to square one (not starting without the help of pouring petrol down the carbs).

    I’ve reset the mixture screws 1st time starting at 1.5 turns and then doing quarter turn there on. 2nd reset was from 2 turns going out from half turns. Then from half turns to quarter.

    I’ve noticed that when I get to about 3 and a fraction turns out, it dies.

    I may being doing something wrong, I’m unsure as it’s my first time fooking around with carbies. Is there anything else apart from the mixture and float level that may be effecting it?


    Sent from my iPhone using Tapatalk
     
    Forky, Jun 9, 2018
    #22
  3. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,233
    Likes Received:
    1,423
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    When you say nothing - drops off idle and stalls - even when it's just idling the pump should click periodically.

    Won't start - once the carbs are well adjusted they need choke to start.

    BTW those measurements with the float height and fuel level are spot on

    Anything else been done to the carbs? keyster kits or anything else changed?
     
    ruckusman, Jun 9, 2018
    #23
  4. Forky

    Forky Active Member

    Messages:
    45
    Likes Received:
    17
    Trophy Points:
    78
    Joined:
    Apr 13, 2018
    Gender:
    Male
    Location:
    Brisbane
    My Bike:
    1990 Yamaha FZR250r
    I have used full choke and it doesn’t really help all that much. Some times it will help get the engine running and most times it does nothing


    Sent from my iPhone using Tapatalk
     
    Forky, Jun 9, 2018
    #24
  5. Forky

    Forky Active Member

    Messages:
    45
    Likes Received:
    17
    Trophy Points:
    78
    Joined:
    Apr 13, 2018
    Gender:
    Male
    Location:
    Brisbane
    My Bike:
    1990 Yamaha FZR250r
    The pump is working fine. I’ve held my hand on it to feel the pumping.

    I haven’t used any kits on it.


    Sent from my iPhone using Tapatalk
     
    Forky, Jun 9, 2018
    #25
  6. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,233
    Likes Received:
    1,423
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    OK only other thing I can think of is the balance between the carbs - obviously it's not easy to keep running to do it with a carbtune or the like.
    So you can do it with a small drill bit - wind up the idle to get underneath either number carb 2 or 3, (forget which) - then adjust the others to the same.

    Once done wind the idle back down

    Is the airbox installed with the filter and lid?
     
    ruckusman, Jun 9, 2018
    #26
  7. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

    Messages:
    10,929
    Likes Received:
    6,720
    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
    Heres the 3 problems you have

    Its a 30 yr old bike
    Its an FZR250 3LN1
    It has 4 inline carbys

    I have had one for 4 years and it still doesnt run 100% ... close but not perfect .... and I know what Im doing ... kinda :lolsign:

    This forum is full of 'inline 4' carby problem posts .... and they continue

    The carbys WILL need a full rebuild with Litetek kits and new emulsion tubes /needle jets and properly cleaned (especially jets and all orifices) as per the many posts/threads about on this subject

    But if its 'starting' from fuel chucked down the carby throats then lets go back to the beginning of the fuel delivery system ....

    Theres a vent in the cap that stops a vacuum forming as fuel leaves the tank
    Theres internal filters inside the tank where the fuel outlet is
    Theres o rings and such inside the fuel tap
    Theres should be a fuel filter running from the tap to the pump that is one directional

    First thing to do is to pull off the fuel hose at the carbys and turn on the pump (with a container under the hose end) and check for fuel flow


    Stick with it ... its worth it in the end .... :thumb_ups:
     
    • Like Like x 1
    GreyImport, Jun 9, 2018
    #27
  8. G1D1

    G1D1 Active Member

    Messages:
    39
    Likes Received:
    21
    Trophy Points:
    178
    Joined:
    Aug 16, 2017
    Gender:
    Male
    Location:
    Sydney
    My Bike:
    FZR 250 3LN3
    I’m having almost exactly the same problem with a 3LN3, however mine won’t start at all without fuel down the carbs. I’ve rebuilt carbs with keyster kits.

    I’ve checked fuel filter, tested pump and checked that fuel is filling each bowl on the carbs. Checked float heights and set mixture screws to 3 turns out. Might test a few changes to mixture screws.

    Would be very interested to hear the outcome of this one @Forky
     
    G1D1, Jun 9, 2018
    #28
  9. Forky

    Forky Active Member

    Messages:
    45
    Likes Received:
    17
    Trophy Points:
    78
    Joined:
    Apr 13, 2018
    Gender:
    Male
    Location:
    Brisbane
    My Bike:
    1990 Yamaha FZR250r
    I have the fuel tank off and just have a bottle connected to the fuel hose going into the pump.

    I might either get a replacement carb and piss this one off or get a new kit.. more leaning towards the new carbs


    Sent from my iPhone using Tapatalk
     
    Forky, Jun 9, 2018
    #29
  10. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

    Messages:
    10,929
    Likes Received:
    6,720
    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
    Ill repeat myself .... have u had the hose off the carbs to see if the pump is actually pumping?

    And Ill repeat myself once more ... new carbs ? ... what are they ?? .... EVERY set of carbs will need an overhaul and then adjusted/tuned when on the bike

    We had an FZR here and when we bought it were told 'mechanic had 'done' the carbs' ... yea done alright ... done a dodgy ..... they were untouched inside but had a nice coat of grey/silver paint on the bodys to look 'reconditioned '

    :headbang:
     
    GreyImport, Jun 9, 2018
    #30
  11. Forky

    Forky Active Member

    Messages:
    45
    Likes Received:
    17
    Trophy Points:
    78
    Joined:
    Apr 13, 2018
    Gender:
    Male
    Location:
    Brisbane
    My Bike:
    1990 Yamaha FZR250r
    Yes obviously I’ve checked the fuel pump.

    And I know you can’t get brand new spanking carb. It’s just my way of saying, I’ll get new carbs to the bike..


    Sent from my iPhone using Tapatalk
     
    Forky, Jun 9, 2018
    #31
  12. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

    Messages:
    10,929
    Likes Received:
    6,720
    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
    giphy.gif
     
    • Like Like x 1
    • Funny Funny x 1
    GreyImport, Jun 9, 2018
    #32
  13. Forky

    Forky Active Member

    Messages:
    45
    Likes Received:
    17
    Trophy Points:
    78
    Joined:
    Apr 13, 2018
    Gender:
    Male
    Location:
    Brisbane
    My Bike:
    1990 Yamaha FZR250r



    Sent from my iPhone using Tapatalk
     
    Forky, Jun 9, 2018
    #33
  14. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,233
    Likes Received:
    1,423
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    We all know the frustration, so you're amongst friends who've been there done that.

    You've done a good job with the float heights, fuel level so you can rule that out...
    stick with it - perhaps check some basic things such as blocked/clogged jets.

    If you don't have compressed air to blow through them then some copper filaments out of some power cable is nice and soft to avoid damage and thin enough to get through the smaller ones which are the most likely candidates to be blocked.

    Depending on what you've done to them thus far, it's worth double checking anything you've done

    Most of the Fizzer carbs get litetek kits through them c/o @maelstrom and the full clean in the process,
    https://www.litetek.co/Carb_Kit_Yamaha_FZR250_3LN1.html

    Worn emulsion tubes and needles usually cause the most problems with chugging and refusal to rev at idle, but doesn't seem your problem,
    the fix is then keyster kits 2 for the inners
    https://www.motorcyclespareswarehouse.com.au/products/k-1205yku-ky-carb-repair-and-parts-kit
    and 2 for the outers
    https://www.motorcyclespareswarehouse.com.au/products/k-1205yks-ky-carb-repair-and-parts-kit
     
    • Like Like x 1
    ruckusman, Jun 9, 2018
    #34
  15. Forky

    Forky Active Member

    Messages:
    45
    Likes Received:
    17
    Trophy Points:
    78
    Joined:
    Apr 13, 2018
    Gender:
    Male
    Location:
    Brisbane
    My Bike:
    1990 Yamaha FZR250r
    Just a quick update,

    I’ve pulled the carbs apart to inspect and clean one last time before I give up. Drained the fuel from the floats into a bowl and noticed there was a lot of **** in it that could have potentially blocked a jet or other.

    After a quick look, I’ve noticed the needles settings go 3,2,3,2. I’ve also noticed that two o rings on the diaphragm side are missing on 1&2 carb.


    Sent from my iPhone using Tapatalk
     
    Forky, Jun 10, 2018
    #35
  16. Forky

    Forky Active Member

    Messages:
    45
    Likes Received:
    17
    Trophy Points:
    78
    Joined:
    Apr 13, 2018
    Gender:
    Male
    Location:
    Brisbane
    My Bike:
    1990 Yamaha FZR250r
    3&4 have the same size 102.5 and 1&2 are 90. The ones below it are all the same at 37.5 is this correct?

    027bb8619cd0657540ba5582af5ab969.jpg



    Sent from my iPhone using Tapatalk
     
    Forky, Jun 10, 2018
    #36
  17. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,233
    Likes Received:
    1,423
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    ruckusman, Jun 10, 2018
    #37
  18. Forky

    Forky Active Member

    Messages:
    45
    Likes Received:
    17
    Trophy Points:
    78
    Joined:
    Apr 13, 2018
    Gender:
    Male
    Location:
    Brisbane
    My Bike:
    1990 Yamaha FZR250r
    Cheers man



    Sent from my iPhone using Tapatalk
     
    Forky, Jun 10, 2018
    #38
  19. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,233
    Likes Received:
    1,423
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    • Like Like x 1
    ruckusman, Jun 10, 2018
    #39
  20. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

    Messages:
    4,737
    Likes Received:
    2,883
    Trophy Points:
    943
    Joined:
    Mar 18, 2014
    Location:
    Sydney NSW
    My Bike:
    FZR250R 3LN6
    Those diaphraghm o-rings are absolutely critical as well. Luckily they come in the litetek kits.
     
    • Agree Agree x 1
    Linkin, Jun 10, 2018
    #40
Page 2 of 3

Share This Page