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Project ‘89 FZR250r 3ln1

Discussion in 'Your 250cc Projects' started by Brandon Otte, Jan 8, 2021.

  1. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    It really isn't difficult and it's exactly what you do to balance them with a Carbtune or equivalent manometer, except that in that case you're struggling to do it with the engine running and finding the adjustment screws whilst burning your fingers

    With the carbs removed for cleaning:
    First step is to check before adjustment, they may not need any adjustment at all, to check them, use the idle adjustment to get #3 to just accept whatever wire you've decided to use - then check the others

    One tip, between adjustments for each cylinder you flip the throttle to check that it's all seated, then re-check

    On the bench - 20 minutes should be mote than enough
     
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  2. Brandon Otte

    Brandon Otte Active Member Premium Member

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    @ruckusman I’ve got her running so I can ride it without gunning it, pulls okay under 10k but I’m pretty sure it’s only running on 3 cylinders most the time or just not right, so question:
    Can I remove the carbs, open them up, clean them and reassemble without needing to set float levels, mixtures, synchronising etc etc etc?
    The more I think about it and the more I read greyimports threads the more I realise how intricate and sensitive these carbs are.
    I mean I’ve got it running from not at all with replacing the fuel and a few squirts down the carb throats. I can imagine though that the insides are all ‘jammy and gunked up’
     
  3. Brandon Otte

    Brandon Otte Active Member Premium Member

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    :D:D:D:DLooking damn good C96B7C97-523A-4B77-9240-80CC14075797.jpeg
     
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  4. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    @ruckusman
    Im going to disagree on the syncing
    I have always been under the impression #2 is the base carb (for those that dont know , while sitting on the bike , cylinders are from left to right numbered 1 to 4)

    carb #1 and #3 are synced to #2 , then #4 to #3
    I use a very thin guitar string or a very thin feeler gauge

    @Brandon Otte

    Simple things first

    Make sure the inline fuel filter is clean ... pull it off and tip out the fuel and see if its "dirty"

    Check that the choke lever is operating the choke plungers on each carb (the plungers can "fall out" or come detached from the rail )

    Check the EXUP is working and adjusted correctly

    https://2fiftycc.com/index.php?thre...-powervalve-information-and-maintenance.1099/

    Check the plug caps are ok and the leads and make sure the coils are connected correctly

    https://2fiftycc.com/index.php?thre...eads-spark-plug-configuration-inline-4s.8176/

    https://2fiftycc.com/index.php?threads/trim-your-spark-leads.8032/

    Check what the mixture screws are set at .... standard starting point is 2 turns out
     
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  5. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK, so that it doesn't intimidate you, before you pull them off, check the fuel levels - that's important

    I can understand your reticence in not wanting to go about adjusting anything internally - THAT is the correct attitude and why you must check the fuel level.

    If you want to leave that as is, then it's OK, but KNOWING the fuel levels will be important at some stage if you're chasing poor running.

    IF you want to clean the float bowls, then you're removing the carbs, check and adjust the balance as necessary - sounds like it's more difficult in your mind than it is actually doing it.

    Adjusting the balance will be important at some point, bench sync is the NICE way to do it, not as precise as with a manometer and you can see visually what you're doing - BONUS

    The problematic cylinder may be a spark plug, simples
    You have the instructions for trimming spark leads art the plug end - simples

    Spraying some carb cleaner through the air jet inlets in the throats may be helpful.

    The carbs aren't especially SENSITIVE very much unlike some of the women that I have been unfortunate enough to have in my life, they just have to be done correctly for best performance.
    There are pages and people here to make certain that you do them correctly IF they need adjustment
    First you have to measure...
     
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  6. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Perfect @GreyImport - more than happy to be corrected, been a long time since I did it and I glanced at the pic you kindly posted on the previous page

    The rest is just a logical process
     
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  7. Brandon Otte

    Brandon Otte Active Member Premium Member

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    I’m going to hold off on removing the carbs for now. I did check the filter when the tank was off and it’s like new, clean and clear. The EXUP is A-ok. I just started her up and found #1 cylinder isn’t firing at all!!! Used my thermo gun and just a quick touch of all the headers.
    So I need to check the spark.
    I’ll pull the fairing and remove that lead and see what I find. It explains why it sounds like a 3 cylinder.

    3425D2C5-978C-4928-B9D1-0151CC3D3041.jpeg 776BADCC-EA33-408E-AACA-74E550F18930.jpeg
     
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  8. Brandon Otte

    Brandon Otte Active Member Premium Member

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    Spark plug and lead are in pristine condition, plenty of spark. Drained #1 carb a few times because it was easy with the fairing off and is now warming up(the header) but still missing most the time so alas I will be cleaning those carbs just like I’ve been told haha
    @GreyImport its as though you’ve done this before
    :bowdown:

    1E32DA5D-3844-4A7E-A9AD-98A6FD066882.jpeg
     
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  9. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Check your fuel levels before you remove the carbs - then and only then if they aren't correct you can adjust the float height

    I always face palm when people just start bending the float tangs to adjust the float height without knowing what the fuel level was to start with

    https://2fiftycc.com/index.php?threads/my-fizzer.872/page-32#post-15537

    @my67xr can chime in with mixture screw adjustments - he's a guru

    Basically put everything back to where it should be

    When you have the carbs off - check main jets - larger outer smaller inner - this can and does get mixed up
    Needle settings are also different between the inner pair and outer pair

    https://www.2fiftycc.com/index.php?threads/3ln1-float-heights.10023/#post-113520

    Note depending on which needles you have, the table in that post may confuse you

    3LN1 can have all 4 needles 5CT7 AND the inner pair of carbs have a 0.5mm shim underneath - all 4 needles on the 3rd clip

    OR

    They can have 5CT7 on the outer pair and 5CT9 on the inner pair - with all 4 needles on the 3rd clip

    Holler for assistance if confused on any of the above
     
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  10. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Yes once or twice ..... and to be honest my 3LN1 has never run 100% correct :lolsign:

    Did u just run it stationary or out on the road? ..... if it was me I would get it warmed up and give it the beans on road
    Ive had them running sweet and starting first go in the workshop , then no go out in the real world
    As then the next servicable item can be the valve clearances .... another can of worms :D
     
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  11. Brandon Otte

    Brandon Otte Active Member Premium Member

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    Stationary and on the road. Oh dear don’t even mention valve clearances! When I had the tank off and it running by just spraying petrol with a squirt bottle it ran mint on all 4 pots. So pretty sure it’s just the carb. I may just try that again, it’s cleared out the other 3 carbs so surely there’s a chance.
     
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  12. Brandon Otte

    Brandon Otte Active Member Premium Member

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    @ruckusman can I clean the carbs with threebond or carb cleaner just from the carb throats without removing them at all? Or even remove the float covers while they’re still on the bike and spray carb cleaner in there?
    I mean how far apart can I take them before I need to ‘retune’ them? From the way it’s running atm It’s like 3 cylinders are mint and just that #1 hasn’t quite come right. I’d rather try my luck with a cleaner sprayed in from externally first... because I’m apprehensive about taking on the carb rebuild
     
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  13. Brandon Otte

    Brandon Otte Active Member Premium Member

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    Here’s a quick video of what she sounds like atm.

     
  14. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Definitely try the external methods first, however the screws for the float bowls should be sufficiently tight that removing them with the carbs in situ will be difficult

    Please do yourself a favour and measure the fuel height because if they have been 'tuned' by the P.O. the floats may have been adjusted and that can be done at the same time as using the drain screws to flush the float bowls - win win

    Literally the only adjustment on them is the fuel level/float height - the rest, if dealing with an unknown quantity is checking what has been done by the previous owners as simple mistakes make big differences

    Those little mixups can make big differences, for example reversed main jets will make it difficult to get past 10K RPM, I believe it was @my67xr that discovered the incorrect jets in the corresponding boxes of the keyster kits and just that one difference caused all sorts of grief for @Joker when he put keyster kits through his carbs at some point

    Now unless you knew of that error when using the '(in)correct' replacement parts for the centre/outside carbs you'd be scratching your head in frustration...

    They aren't so sensitive or delicate that methodical disassembly and reassembly is going to change anything - that one misfiring cylinder may be a blocked air jet which a spray carb cleaner will potentially correct.
     
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  15. Brandon Otte

    Brandon Otte Active Member Premium Member

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    Quick update, haven’t had time yet to give the carbs a spray with cleaner but just started her up again and is definitely clearing up so to speak. Firing on all 4. Am still holding onto hope that I’ll get away with a ‘non-invasive’ carb clean.
     
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  16. camarda

    camarda Active Member Premium Member

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    Hey Brandon,

    Don’t fear the carb rebuild, it’s not as daunting as it seems. These guys helped me through it and now I know the carbs back to front. Read through those threads and you’ll be fine. It’s basically. Put the right jets in the right spot. Put the right needles in. Put the needle clips in the right spot. Turn the idle mixture screw the right number of turns. Check fuel level. Set float to right height. Check fuel level again.
     
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  17. Brandon Otte

    Brandon Otte Active Member Premium Member

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    @camarda yeah thanks for that I’ll definitely be giving it a shot in the near future. I’ll order the litetek rebuild kit first and wait for that to arrive.
    Took her for a ride yesterday and gave it the beans, at part throttle it’ll rev right up quite smooth but as soon as I give it anything more than about 1/4 throttle it bogs for a while before picking up. Not keen on leaning out and doing any permanent damage so the clean/rebuild is a must.
     
  18. camarda

    camarda Active Member Premium Member

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    At least check that all the jets are in the right order and the needles are correct and the clip positions are correct for now. Mine had all of those things wrong but it was all clean. Swapping the jets into the right position and putting the correct needles in with the right clip positions made it run perfect.
     
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  19. camarda

    camarda Active Member Premium Member

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    Oh and also setting the correct fuel level is crucial.
     
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  20. Brandon Otte

    Brandon Otte Active Member Premium Member

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    Hi everyone,

    So my 2kr wouldn’t start today, eventually did but running on 3 cylinders. Checked which cylinder with the infrared gun and pulled the plug. Sparked fine on a test fire but was suspicious it has suddenly started playing up, yesterday had it running and was perfect. So tried a plug from my 3ln1 and it suddenly started running on all 4 but missing under any load. Mucked around a bit and pulled the ignition lead out of the plug cap accidentally, put it back together and test rode it - was very intermittent, firing then missing etc. Could hear what I think is it sparking/earthing somewhere other than the plug. Very frustrating considering I had all my riding gear on and trying to pull plugs with the fairings still on. Anyway I must add my 2kr is sitting outside since buying the 3ln1 as there’s not enough space in the garage. Last night it absolutely bucketted down with rain and I’m wondering if that has anything to do with it. I’ll be buying a new set of plugs tomorrow and testing. Fingers crossed that does the trick and it’s not a coil or otherwise.
    Got me thinking as well though that my 3ln1 miss fires on just the 1 cylinder atm(probably is just the carbs as we’ve been talking about) but... I’m going to throw a fresh set of plugs in it just to be safe. Any ideas?
     

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