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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

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    carbide ground to fit me cutter slots, better go mates and braze em in. got no gas. grr.
    ummmm.
    whilst poking the burr in the pockets i sorta noticed something as it cleaned up...

    heres a normal seat, or what i regard as a "decent" seat... would grind that and be happy.
    20231003_102715.jpg

    and this is what i suspect the whole drama really is...
    20231003_102700.jpg

    they all vary, but this is the worst at what looks like 1mm at least.

    really nasty lip there, but it isnt valve recession, as it doesnt contact there. looks machined in from factory.
     
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  2. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    That second seat does look a bit iffy by my eye.

    By the way, I was working on an MC22 engine for a customer at work. He had over-revved it and bent two valves. It also needed some thread repairs for the valve cover threads, and the timing gear set. Head had to come off, luckily he supplied a new gasket.

    I tried the neway 'gizmatic' to cut the valves, but they were too small and I couldn't cut them at all. Had to settle for a lapping job on two valves from a spare head, as the customer was on a budget.

    He didn't come back complaining so I'm assuming all is well.

    I hope you succeed with these cutters and have a nicely running bike at the end.
     
  3. gyro gearloose

    gyro gearloose Active Member

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    dubious. is it possible to over rev an mc22?

    lol.

    ok. brazed. bit ugly. tip to self... grab the right filler rod. or make sure ALL the carbide is pretinned...

    20231004_094701.jpg
    couldnt help myself. quick sharpen by eye on the benchgrinder with the 60degree... shoved it in and gave it a spin...

    with the inevitable chatter but... took a few seconds to get rid of that lip... fugly but still a lot better than what the factory left!

    20231004_092743.jpg

    and well, i guess i gotta mount this as its my only "precision" diamond wheel...

    20231004_092849.jpg

    a cup wheel is probably better... this will do for now. once sharpened properly, if they chatter, i might try making some laps as well, grind it our or yeah... got no issue redoing these,fw improvements to be made...

    can pop the guides out... whats that, 8mm or so? easy, and rigid. this 3.5mm is nonsense really. dont want to but its the best option?
    use a standard taper for the arbor and cutters so i can use a standard reamer for a bit better accuracy... ie, MT0 or something.
    use lathe inserts. still gotta braze em. at least, the tiny lil 30 degree one does...
    cut the seats as notches from the side rather than try a 2mm slot again...
    make sure i got one type of silver... lol.

    right. get off the puter.
     
  4. gyro gearloose

    gyro gearloose Active Member

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    actually, regards the neway gizmatic and removing the guides... that really should maybe be the whole plan of attack. profiled carbide blade and a decent rigid bar... hmmm.

    whatever. finish these and if they dont work i got a whole new plan in mind...
     
  5. gyro gearloose

    gyro gearloose Active Member

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    well. at this point? laugh? cry?

    laugh. things are looking up.

    so, i went to lap the valves, and of course had that genius moment... seals...diamond grit...

    popped the seals off expecting them to be no issue.
    ha ha. none survived. whatever. order some more!

    why didnt anyone inform me about the 2kr having 4mm stems?
    as well as the 400. and 600. all share the same seal. 1hx 1211900.
    3ln? 3ln1211900... sigh. do the cheap chinese ones fit? worth a shot. only listings for the genuine OEM im finding have the 1hx shown for the 3ln and yeah... not cheap.

    anyway! that does... change things for future mods... like... turned down 400 valves in oversized seats... a good excuse to get that unused lathe converted to cnc, make guides. whatever. idle musings.

    a damn setback though, i have to wait for valve seals. sigh. put everything in a box, back on the shelf...

    so i just tore the head off another donk. why not huh?

    cough cough. lost a shim. dropped two exhaust buckets. dont get carried away looking at combustion chambers until the cams are back in! effin!

    not too worry, shell turn up, got heaps. gotta check clearances and clean it down a bit first anyway.

    this things valves are perfect. seats are perfect. i can see one valve has shouldered a bit, worth looking at in the future, but right now? its in degreaser, and im shoving it back on tonight cus its pristine other than the obvious blown rings on this unknown history engine... looks to be stock.

    it definitely doesnt have pockets the same diameter as the valve itself cut into the seats.

    one cylinders sorta what youd expect...dry.
    20231008_183625.jpg
    three are an oil soaked mess. :) just what i like to see. blown rings.
    20231008_183728.jpg

    anyway. all valves are definitely riding with the rim slightly proud of whats flat if its not 30. nice shiny contact bands.
     
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  6. gyro gearloose

    gyro gearloose Active Member

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    vrooom!
    should have done this a long time ago...

    effing mechanic wouldnt log in... "ive knocked off"... fine. rego tomorrow.

    good fang down my local... ahem... testing ground. the last of the "unlimited" zones. yep. theres still one or two in sydney ;) no lights, no lines, no signs, rural, its 100. wish i had pinched the black circles from lower mcdonald way back, before they took em down. (end school zone to unlimited always floated my boat...)

    needs a balance, the pilots are all over the shop, one of the EXUP cables is frayed badly, one of the coolant o-rings under the carbs there is weeping as always, and last years fuel probably doesnt help...

    fired up first go. yay! no smoke.

    and after half an hour of idling, revving, riding... no chuggers yet.

    i realised that my frames been restamped! someones done the naughty naughty... joys of old bikes huh? this might not be a 3ln3 frame... 3ln-285*** under the 3ln-280***. shhh. dont mention it to the mechanic ;)


    so? pink tank or white for the black bodywork? decisions decisions...
     
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  7. KiwiMat

    KiwiMat Well-Known Member

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    Ha... spray the pink one black/grey. it didnt have any holes init from memory. i think the white one was holy... Well earned for doing my valve clearances, or rather undoing them to work off the chug carbon.....
     
  8. gyro gearloose

    gyro gearloose Active Member

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    shaddup you! still got rust in carbs. new lines, 5 micron filter, new pump, new tank, and a bunch of magnets in the filter.... wtf?

    so... had a gremlin. ignition. dropping 1&4... ive already swapped coils before so, this time... CDI, crank sensor, and pop all teh plugs apart and give em aclean and squeeze em tighter...

    ignition fixed. would actually idle rather than hit 3k and stall (or sound like a boat...) no more popping, crackling, etc.

    for a while.

    i got one good ride after registration.
    and then it got worse and worse. was about to fang it down to wisemans ferry... ha ha... i got 5km...
    chugging came back.

    ride round the block, was rolling the last 1km downhill.
    ride just down the road. 1.5km, dead. picked it up the next morning... 500M.




    EFFING!

    have a break for a few days. tear up the path. clean drains. feels more productive...

    path done, here we go... i know what has to be done. i tried avoiding it, all i did was piss myself off. as usual. always follow your guts! think i would have learnt by now... cutting corners gets you nowhere but the psych ward...

    first up. i need a spring compressor...
    ta da!
    spring compressor.jpg
    next. i gotta pop the head again. i know what im going to find. maybe i should have looked closer?

    it was worse than i thought... i mentioned a valve looked suss?
    stuffed inlet valve.jpg
    well, not just one. havent cleaned em, but i think its all of them at a glance.

    i said them seats looked good?
    stuffed seat.jpg

    i lied :) to myself... sigh. theres that ridge again...

    and after just a few seconds?
    topcut30 seat.jpg
    much nicer. same seat.

    so i guess i better set the grinder up and dress them a wee bit, get that shoulder off...

    then grind em in. leaving the stem seals in place this time...


    oh. something else... its starting to look like the original point of this thread, those slides and inserts having numbers?
    pretty sure it should be 2-1-1-2. the slides are often random, because yeah... who thinks of this stuff? no-one! slides are always getting pulled and played with...

    but you can also assume that NO-ONE tampers with the inserts... or very very rarely. so far, everything ive looked at has had the little nibbed inserts (almost unnoticeable if you dont know of it...) on the inner cylinders, and theyre number 1.

    would be really nice if some people actually started taking the time to verify this slide and throat arrangement. that was what this thread was meant to be about... it just got...sidetracked :)

    so far, no-one has even taken a few minutes to LOOK? only gotta pop the filter, lift the slide and peek at the lower left hand corner of the inserts..


    i think im going to hassle mikuni even if they tell the public to bugger off....
     
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  9. gyro gearloose

    gyro gearloose Active Member

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    FIXED.
    finally.
    or should i say, waiting on new plugs then i can definitively say
    fixed?

    soooo... this looks good. x8...
    20231019_104237.jpg

    this i guess is what one expects to see...
    20231019_192647.jpg

    slap her together.
    do you think it starts?
    oh no.
    cough splutter pop bang splutter...
    did get it fired up... gutless ride up the road... nope... awe hell. seriously? what the hell is it now?

    long hard think... next day...

    was about to slap a compression gauge together...
    just... have another look...

    im retarded. exhaust retarded. one link out. stupid effin... dots on dots but uneven links between sprockets? hmmm... that doesnt feel right...

    and then... im not exactly sure how i did this...

    i got the firing order wrong... :headbang:
    ok... brainfarts fixed.

    at this point. it starts first go. it idles. it blips on the throttle. it screams. it does what a lil I4 is supposed to do...
    this is when you may dance...:party:

    rode. no issues. 150km... cool. it was perfect, other than a tiny stumble on transitions, or that cruise in certain RPM. its been bored, back cut valves, and carbs are now "as stock"... i expect something?
    then...

    needed rescuing at 10pm in drummoyne, didnt i? (cheers kiwi...)
    was going perfect then just crossing gladesville bridge... bang. 1 and 4. ok. this is NOT a COIL... but it is ignition now!

    plugs. and i know what im going to find the next morning. i had my suspicions, this has confirmed it.

    cold, DOA, try starting. nothing.

    pull plugs, sandblast the fuggers.

    VROOM. instant start.

    with one not happy... 3.5cylinders. pop plugs, can see one has this odd little... short on the porcelain. slightly moist looking compared to the other 3.

    open carbs. filter...

    20231022_085040.jpg

    ok. RUST.

    tear that freaking pump out. its the only thing left from the original tank that sprayed rust through everything. this is rust. and its only source is that pump.
    my plugs are getting hot, getting coated with conductive who knows what, and yep... and this stuff aint magnetic, either... just slips past neo magnets without a trace... colloidal ferrous oxide... yummy. current set of plugs had come from the old 2kr... oily but free of rust. til now.

    throwing old plugs in, theyre all contaminated...

    ripped the plugs out of an R6 on the scrapheap, only plugs that havent been in this engine... old, worn, grumpy.

    but its running again. two tanks so far. new plugs on order.

    and now... now having no pump is an issue.

    the filter gets an airlock? gotta reach down and flick it every now and then... it really got me the first time...

    got another one. couldnt be bothered right now...
     
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  10. Mike Green

    Mike Green Well-Known Member Premium Member

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    I know you say it's running sweet and revving clean but I have checked a few heads and on every single one, all the valve springs were overlength when installed. Something to check and easily rectified if found to be overlength installed. Regarding the "powerband" with the exup valve working. I don't have the exup on my bike and the fueling is very odd, which is being charitable. The exhaust is very short stubs into a plenum, the intake is about normal length into a plenum, and cam timing is stock. It's so bad at 9-10,000rpm that it will barely pull through those revs on the dyno. The dip/marker is at 9K and is obvious for all throttle positions
    upload_2023-10-24_13-26-41.png
     
  11. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    If you haven't already, replace fuel filter with a new standard type, my offer still stands if you want one come see me at Flywheels in Tempe.

    Have new CR8E's in stock too

    I would definitely ditch the fuel pump as well, it's a paperweight now with all the rust through it. Can be replaced with a simple vacuum fuel tap anyway which also does away with the manual fuel tap too. Will help eliminate flooding as with no vacuum there is no fuel gravity flowing into your carbs.

    Other ignition bugbears, the leads and caps start to go. Internal corrosion and the exterior sheathing starts to split and no longer insulates, spark arcs out to frame or cylinder head etc.

    I would like to ride an FZR250 again, maybe after I could give you an opinion about yours.
     
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  12. KiwiMat

    KiwiMat Well-Known Member

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    Somebodys 2kr courier bike..... Gyro..?
    20231030_191401.jpg
     
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  13. gyro gearloose

    gyro gearloose Active Member

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    tempe hey?
    i vaguely recall buying this around that way somewhere...

    revving clean... i wouldnt say that. its not...right. close. but not there.

    new set of plugs and it is a different bike now. starts first go, idles. theres just that bit of grumpiness, 3rd gear at 60... odd transition stumble. meh. but three tanks, only issue is the reserve filter airlock nonsense. definitely rich somewhere but rather ride than bother now :)


    looking at the coils from the R6...

    no! other projects! if i wrote this list down...

    from landscaping to hydraulic technician to welder to bricklayer to farmer chasing chickens to getting stoned... its varied :)
     
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    Last edited: Nov 4, 2023
  14. gyro gearloose

    gyro gearloose Active Member

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    it does look familiar...

    20231104_100517.jpg
     
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  15. gyro gearloose

    gyro gearloose Active Member

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    well, i guess its time for an update.

    had a bit of an issue with the boots. despite swapping coils three times, i ended up with the arcflashed boots. sorta knew all along but what with the other gremlins...

    right. swap them over... along with, this time... cr8ek.

    and...

    five tanks later, still no issues. instant start, no chugs (mmmmm... it doesnt like sitting in the sun all day though? that does make it have a little grumble. vapor lock type thing. barely notice).
    quite happily breaking speed limits. (on private roads, of course!) and revving clean all the way to redline.
    might pop the 3ln1 jets in, as it does feel a tad lean... my memory of CV tuning was if it picks up a bit when you back off slightly... its lean. yeah. it doesnt mind WOT, but you do feel the pick up if its rolled off just a touch.


    plan is now to rip the head off that 3ln1 next to the 2kr, give it a service, throw it on kiwimatts 3ln1, which has had no carb work done yet but suffered the chugs (the one that got better when we set the valves sloppy and is now grumpy again)

    at which point, if the chugs are gone, its 100% conclusive. this "carb issue" is the valves.

    i gotta make a jig first. dont hold your breath ;)
     
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