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

Help I found something weird... 3LN3

Discussion in 'Yamaha 250cc In-Line 4's' started by gyro gearloose, Mar 7, 2023.

  1. gyro gearloose

    gyro gearloose Active Member

    Messages:
    100
    Likes Received:
    94
    Trophy Points:
    128
    Joined:
    Feb 27, 2023
    Gender:
    Male
    Location:
    sydney
    My Bike:
    variable
    A cantankerous 3ln... 3?
    So, a new set of diaphgrams turned up today.
    Im looking at the slide and i notice a number moulded into it...1. Up the top...
    Um?
    Looked at the others... 1. 2. 2....
    Um.
    The body inserts?
    Theres a 1... theres a 2.
    It feels the cutaways on the slides are sloped one way or the other... minute, but its there.
    All i see on the inserts is this tiny "bridge" right at the bottom, on #1... May be nothing, may have a drastic effect on transition... iunno! But its there... for a reason.

    Sure didnt see this before... only had them apart five times at least...
    So... anyone ever noticed this?

    Better yet, anyone have a set that havent been tampered with, and can confirm that the slides are matched to the inserts from factory?
    and more to the point, which one is for which cylinder?

    It may very well be crucial.
    its probably nothing...

    I have been having a nightmare with this 3ln.
    Seal kit, full rebuild, ultra sonic cleaner, been over every hole and orifice...
    Everything is as it should be. But this thing has me stumped.

    Before rebuild, if it started, was fine. then it would enter "bog mode", usually after idling for a while.
    Full throttle, choke, barely running... turn fuel off, and it would eventually clear up and behave... until next time.
    Now its a nightmare :)
    That last ride, if i coasted for longer than a few seconds, the stumble on accelerating at 1/4 was terrible.
    One point it nearly cut out entirely... turn fuel off and pray! It cleared up...
    so, sounds like floats? Nope. Got that all spot on.
    i suspected the bungs on the pilot circuit... some goop and hammering them home HARD, and it would start and run flawlessly... for about a week.
    new seals, no change. Worse really. Ffs!

    The genesis never missed a beat...

    Soooo... at this point... one last soak, another buzz in the bath, new diaphgrams and fingers crossed... See in a day or two...

    Also... i found the real emulsion tubes.
    Theyre under the main jet... behind that square seal... they do tap out if ones careful. Mine were clear...
    What everyone calls the ET is the needle jet...
     
  2. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

    Messages:
    4,756
    Likes Received:
    2,901
    Trophy Points:
    943
    Joined:
    Mar 18, 2014
    Location:
    Sydney NSW
    My Bike:
    FZR250R 3LN6
    Welcome.

    As far as I know the diaphragms themselves, separate from the slide, are identical.

    The needle jets and jet needles (what we know as needle and emulsion tube) are prone to extreme wear due to the poor retention mechanism of the needles (only the diaphragm spring, basically)

    Solution is 3YX Zeal needle retainers, or 3LN6/7 slides and retainers. Neither my Zeal or 3LN6/7 models had any wear on the needles or tubes. My 3LN1's and 3LN3's all did, even after replacing them.

    Setting your mixture screws properly may help, 3+ turns out is way too rich, the good range is between 1.5-2.5 turns out as a guide

    3YX Zeal retainers (plastic cup and secondary spring only)

    [​IMG]

    3LN6/7 retainers (cap threads into the slide, the whole slide is required)

    [​IMG]


    Worn out needles and tubes

    [​IMG]

    [​IMG]
     
    • Like Like x 1
  3. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,284
    Likes Received:
    1,451
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    You've got worn emulsion tubes due to the slop of the needles in the slides is your issue

    Solution, keyster kits for the emulsion tubes and DM me with your details and I can send you some brass inserts for the slides to make the hole for the needle a sensible size which should alleviate the needle jet / emulsion tube wear in the future.

    Whereabouts in Sydney are you?
     
    • Like Like x 1
  4. gyro gearloose

    gyro gearloose Active Member

    Messages:
    100
    Likes Received:
    94
    Trophy Points:
    128
    Joined:
    Feb 27, 2023
    Gender:
    Male
    Location:
    sydney
    My Bike:
    variable
    Its not the NEEDLE JETS.
    Emulsion tubes, with the cross drilled holes, reside under the main jet. The "538" tube is a needle jet.
    Besides new keysters, i have thrown all these bits on centers and gone over them with a dial indicator. Theres zero detectable wear or ovality.
    I have been through everything... other than rebuilding the other set.(also dismantled with bits scavenged)
    The diaphgrams are my last ditch effort. Old ones are fine, one has a minor crack at the seal... but its nothing.
    As i said. The slides appear to be matched to the body inserts.
    No-one mentions this.
    It would appear everyone does exactly what i did... pull the things apart willy nilly, throw them back together, never realising the slides and inserts are MATCHED.

    So, who has a set of FACTORY carbs to dismantle and verify? Take a look. See if im talking BS...

    Not really in the mood to dismantle and test the possible combinations of which slide and insert goes on which cylinder.

    The thing is, this issue seems to be across the set, its not just one cylinder. Theres something else afoot besides needle retention methods.

    The bungs really seem to have been the only thing that make a noticeable effect.

    As for bogging and cutting the fuel...
    Strangely, running out of fuel feels exactly the same,and the thing was running lean and hot if boiling half its coolant out was anything to go by.


    The genesis carbs are looking ever so tempting.
     
  5. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,284
    Likes Received:
    1,451
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    Hang on, have you put new keyster needle jets in?

    We chased fuel levels and all sorts of other possible causes for years, chased phantom causes.

    If you look at your needle jets [OEM] through a magnifying loupe you will see wear right at the exit from the needle flopping against the orifice.
    There's 0.075mm clearance right at that orifice opening, needle is 2.515mm and the N8 needle jet is 2.59mm - it doesn't take much wear to make that orifice too big right at the opening, plus the taper starts right about there also.

    Trust me, you've given the perfect description of worn needle jets, bog at idle, throttle pinned and it's running like a diesel and refuses to rev, sometimes won't rev back up whilst riding, I've had all of those things happen in traffic and it sux.

    When it did it to me, the only solution was to turn off the fuel tap, keep the throttle pinned until it livened up.
    Lowering the fuel level by turning off the fuel tap eventually leaned it out till it would rev, then it was take off, tun the fuel tap back on [I forgot to do that many times] and keep the revs above ~4K RPM if possible.
     
  6. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

    Messages:
    4,756
    Likes Received:
    2,901
    Trophy Points:
    943
    Joined:
    Mar 18, 2014
    Location:
    Sydney NSW
    My Bike:
    FZR250R 3LN6
    Boiling coolant is a worry, you may have a head gasket problem there, I had one that did that.

    have you looked at any other aspects? For example the inlet manifolds will go hard and split and cause air leaks... tight valve clearances will cause all sorts of issues but mostly failure to run when hot due to holding the valves open.

    Stretched cam chain will make the engine timing lazy and affect fuelling.
     
  7. gyro gearloose

    gyro gearloose Active Member

    Messages:
    100
    Likes Received:
    94
    Trophy Points:
    128
    Joined:
    Feb 27, 2023
    Gender:
    Male
    Location:
    sydney
    My Bike:
    variable
    I know... ive eliminated every item off the list ive found on here and anywhere. Two sets of oem NJs, neither are worn (i can measure this beyond visuals...) and keysters just made me wait and get annoyed when nothing changed.
    I admit, got the jets backwards. (975/1
    00) All my old aircooled experience was to run the inners richer than the outers... meh, thats not going to effect start n transition...

    Been playing engines since nappies and this one... this one finally has me beaten. I hate having to even ask... im the one thats meant to be answering usually!
    Only done about 1000 since i opened the top. Vaguely recall a few needed swapping. Always aim for that middle clearance...

    Yesh, i am a wee bit concerned about that coolant and gaskets... still, no oily water or watery oil, no strange plug fouling... and it never did it before.
    Probably shouldna ridden but after a year and a half of rego with no running? It started, i rode it!

    Meh. Back together tonight.
    And im going to mess with this slide BS i discovered i guess. Seeing as noone else cares.



    Theyre numbered for a reason...



    20230307_203441.jpg 20230307_203559.jpg
     
    Last edited by a moderator: Mar 8, 2023
  8. jmw76

    jmw76 Well-Known Member

    Messages:
    1,172
    Likes Received:
    602
    Trophy Points:
    498
    Joined:
    Mar 12, 2017
    Gender:
    Male
    Location:
    Melbourne, Australia
    My Bike:
    Honda cbr250rr mc22 road + 1 track, Honda RC 162 tribute bike, Honda Spada Vt250, Honda CBR900RR
    I gather you are talking about the numbers that are in cast/moulded parts. I would be very very surprised if these were some sort of matching marks.
    More likely, these are production marks to identify which cavity from a family tool the parts were cast/moulded in. Fairly common practice to track down production quality related issues and to work out which tool might need some maintenance.

    Peter.
     
    • Agree Agree x 1
  9. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

    Messages:
    4,756
    Likes Received:
    2,901
    Trophy Points:
    943
    Joined:
    Mar 18, 2014
    Location:
    Sydney NSW
    My Bike:
    FZR250R 3LN6
    He may be right though. Many parts are numbered for their respective location. The giveaway is that they usually have different part numbers to their neighbours. I'm not sure that's the case with these slide housings.

    Gyro I get your frustration with these carbs, I have been there myself many times.

    I think it would be worth your time getting some pictures and or video of your problems with the bike running. Some good closeups of the needles and needle jets too.

    You might want to identify which model carbs you have as well. The idle adjuster is different between 3LN1/3+ and the float bowls are different on 3LN6/7 to 3LN1/3/5.

    The jet housings also differ between 3LN1 and 3LN3+

    3LN1, 3LN3/5 and 3LN6/7 also have different jetting as I'm sure you are aware.

    The point is bits get chopped and changed due to the age and grey import nature of these bikes.

    I'd be keen to get an eye on your bike as well, where abouts in Sydney are you located?
     
  10. jmw76

    jmw76 Well-Known Member

    Messages:
    1,172
    Likes Received:
    602
    Trophy Points:
    498
    Joined:
    Mar 12, 2017
    Gender:
    Male
    Location:
    Melbourne, Australia
    My Bike:
    Honda cbr250rr mc22 road + 1 track, Honda RC 162 tribute bike, Honda Spada Vt250, Honda CBR900RR
    Gyro, you are not going to get a better offer than the one from Linkin, to personally come out and site your problems.
     
    • Agree Agree x 1
  11. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

    Messages:
    4,756
    Likes Received:
    2,901
    Trophy Points:
    943
    Joined:
    Mar 18, 2014
    Location:
    Sydney NSW
    My Bike:
    FZR250R 3LN6
    Also if it's not fouling plugs and they aren't black with carbon and wet then the issue might not be with too much fuel, but rather too little.

    You should check the condition of the fuel tank and the strainer on the fuel outlet, clogged with rusty gunk? Fuel flow problem. Replace any inline filter with a new one of the correct type, NOT the generic super cheap auto clear style ones - they clog super quick as I found out.
     
    • Agree Agree x 1
  12. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,284
    Likes Received:
    1,451
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    The suggestions about possible fuel flow issues are very good.

    Running with or without a fuel pump?

    Of the two round jets on the jet housing they can be in the incorrect positions.
     
  13. gyro gearloose

    gyro gearloose Active Member

    Messages:
    100
    Likes Received:
    94
    Trophy Points:
    128
    Joined:
    Feb 27, 2023
    Gender:
    Male
    Location:
    sydney
    My Bike:
    variable
    bdm bdm bdm...
    sigh.
    back together.
    splutter splutter splutter, WOT, fuel off...
    VROOOM!
    fuel on... splutter splutter splutter...

    instantaneous.

    so, right now, carbs are half stripped... but...

    i think i have it solved. the whole stinking issue.

    THE FREAKING BRASS NUT AND WASHER!!!

    checked levels whilst its running...

    when the fuel level is slightly below the angle of the bowl, it clears up. i found you cant actually set the fuel level this low, the tangs are touching the needle valves...
    as soon as the fuel gets over that angle... splutter splutter.


    pop em out, take a bowl off, put em back in, see how they sit...

    that nut is semi submerged at the ideal fuel level.

    i was very gentle on those brass nuts this time.

    theres no seal under there.
    theres a reasonably large gap between needle jet and jet block... enough to see it wriggle. and fuel sloshing in the gap...
    we dont torque it up as we bust a nut :confused:
    i doubt any of us try annealing the washer, or using copper ones...

    ITS SUCKING FUEL WHEN SUBMERGED< AND AIR WHEN IT ISNT.


    im just hunting down that pack of microscopic o-rings i know i had... when i find it, will only have 3...

    i got some teflon rod. sigh. washers?

    get lazy and wrap some tape around the thread :)

    i guess i will update tonight... im meant to be doing something else entirely! grrrrrrrr!
     
    • Like Like x 2
  14. gyro gearloose

    gyro gearloose Active Member

    Messages:
    100
    Likes Received:
    94
    Trophy Points:
    128
    Joined:
    Feb 27, 2023
    Gender:
    Male
    Location:
    sydney
    My Bike:
    variable
    bolt... bolt. not a nut.

    other thoughts... those needles pictured are just... WTF?

    as in... if i have these issues with perfect needles and jets, how did that bike even keep running to get the needles to that point?

    not every fzr is having these issues... so i just remain sceptical about the wear having a major impact.

    the best test for them is to shove the needle in the jet and blow through them. shame i dont have any worn ones to compare...

    right. im off.

    ill be baaaaack.
     
    • Like Like x 2
  15. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

    Messages:
    5,124
    Likes Received:
    3,490
    Trophy Points:
    1,148
    Joined:
    Dec 23, 2012
    Gender:
    Male
    Location:
    Thailand
    Home Page:
    My Bike:
    Yamaha FZR400 3TJ1, Honda MC22
    I agree. A long time ago, in a thread, far, far away, this "chugging" issue was the centre of the universe. I doubted it was the needles and jets because of the sequence of events that had occured. I thought it was the merge bung o-rings. Now your discovery fits better into the correct solution.
    5 psi of air pressure, soapy water and a brush to check the seal of the brass washer and nut before assembly and the mystery of the ages might finally be solved.
    So, new copper washers?
     
    Last edited: Mar 11, 2023
  16. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

    Messages:
    4,756
    Likes Received:
    2,901
    Trophy Points:
    943
    Joined:
    Mar 18, 2014
    Location:
    Sydney NSW
    My Bike:
    FZR250R 3LN6
    Don't those brass bolts have a captive brass washer with them? I swear I could recall them having a washer. My original 3LN did have a dodgied up bolt in the way of a 6mm philips screw in place of the original, with the centre drilled out to make room for the needle.

    If the jet housing is not fully seated and sealed I can definitely see that causing problems with fuel metering.

    Worth noting that sometimes the slide housings are difficult to get properly set, and then the needle jet doesn't sit in its' proper position. In that case the brass bolt will be tight, but neither the slide housing, needle jet or jet housing will be properly seated in their correct positions.
     
  17. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

    Messages:
    5,124
    Likes Received:
    3,490
    Trophy Points:
    1,148
    Joined:
    Dec 23, 2012
    Gender:
    Male
    Location:
    Thailand
    Home Page:
    My Bike:
    Yamaha FZR400 3TJ1, Honda MC22
    Yes, they have a brass washer, but an annealed copper jobbie should offer better sealing.
     
  18. gyro gearloose

    gyro gearloose Active Member

    Messages:
    100
    Likes Received:
    94
    Trophy Points:
    128
    Joined:
    Feb 27, 2023
    Gender:
    Male
    Location:
    sydney
    My Bike:
    variable
    i
    think
    this
    is
    it.
    still aint great... but i rode it. and it didnt overheat.
    needs balancing, needs tuning, needs new plugs, and maybe shoving a sniffer up its hole is an idea cus wow, it was gruuuuumpy.

    but it runs.

    give it some throttle, theres this nasty hump, the transitions terrible, and im sure its only firing on 3 below 6k. or only all four when its cruising. was a strange ride, all over the shop. still not used to this bike, either.

    15k, something suddenly wakes up and weee!

    but it runs, and it didnt die sitting there idling.


    teflon washers under the washers. not ideal but it seemed to do it.
    now, to solder the nuts to the washers, to ensure theres no leakage at that point. and find those o-rings. probably need a 7x0.5 or something. probably exactly what i have/had.

    yet i still had to drop that fuel level as low as i dare, about 1/4mm clearance between needle and tang... without changing needles i dont see how i can get it any lower. the o-ring might fix that anyway.



    now, the only thing to really sort out is this slide issue.

    currently 1221.

    give it a synch n tune, and a week and see how 2112 goes...


    sigh. tuning CV carbs. theyre pricks. even at the best of times. not quite the same a vm type slide carb.

    so there you have it. i reckon the main issue is the nut and washer, something hiding in plain sight...
    and that theres something afoot with the slides. hopefully we all find a consensus!

    its pretty easy to see what insert is in which carb... look in the throat and just at the bottom, in a little recess just to the side, look for this tiny, almost unnoticeable lump... that was insert #1 iirc...

    awe hell, forgot to mention. i had rust. bad rust. new tank type rust. didnt realise when i first got it running, and put a fair wack through.

    shoved a new pump in as the last time i pulled them apart, was still rust coming from somewhere. pump the only source left. new lines, 5micron proflow filter, (only stuck a magnet in there the other night) and tap seals, etc. so it hasnt been a fuel flow issue.

    seriously, if this hadnt worked i was planning on tearing the head off and giving it a de-coke-iron oxide... general top end service... strange theories on iron oxide catalysts or spark conductings, and or valve seat issues...
     
    • Like Like x 2
  19. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

    Messages:
    10,931
    Likes Received:
    6,724
    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
  20. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

    Messages:
    4,756
    Likes Received:
    2,901
    Trophy Points:
    943
    Joined:
    Mar 18, 2014
    Location:
    Sydney NSW
    My Bike:
    FZR250R 3LN6
    Buy a pack of these as they are the correct type of filter for this bike: https://www.mcsonline.com.au/vf201

    Your local bike shop might stock them, I know we do (Flywheels Motorcycles in Tempe). Have had MANY a carbed bike with a rusted tank or clogged filter come through the shop for 'carby issues' - almost always ends up being a fuel flow issue or a rusty tank.

    I'm thinking your 5 micron filter might be a bit too fine for a carburetted bike with a rusty tank and may already be blocked up. Give it the old blow through test... any resistance means its clogged or too fine a filter for the task. You can also just remove it entirely for testing.

    Rusty tank will also mean that your breather cap and drain tube will probably be blocked up. I suspect the fuel outlet/strainer on the bottom will be clogged as well.

    How do the bowls look? Any crud? They need to be pristine. The low point in them is where the fuel is picked up by the jets... also where crud, water and rust will accumulate.

    Top end carboned up? Threebond Engine Conditioner. Green and silver can for the petrol stuff. Warm up the bike to temp, spray it straight through the throttlebodies and give it some revs, on all cylinders. Then kill engine, spray up each cylinder and let it soak for 5 mins... Start her up again and watch all the carbon and crap blow out the exhaust. Run the engine until the smoke is gone. Just be aware it may need new spark plugs after, I have killed many old and new sets of plugs doing this.

    The Threebond is also great for soaking carby bits, just don't get it on any rubber or plastic bits... or your hands... or your respiratory system...
     
    • Informative Informative x 1

Share This Page