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Help Does anyone have a 3LN C-stamped conrod for sale?

Discussion in 'Yamaha 250cc In-Line 4's' started by Xavier492, Aug 18, 2018.

  1. Xavier492

    Xavier492 Member Premium Member Contributing Member

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    I am currently rebuilding the 1HX engine out of my 3LN3 FZR250R and need one good condition conrod to match the rest.

    I have tried all the wreckers I know of but only one has an FZR250 engine. As it turns out, the 2KR has a B-stamped conrod that is shorter and lighter than the 3LN's C-stamped conrod.

    I know that most FZR owners have a spare engine - will anyone be willing to sell me a conrod, or know where to get one?

    PS: I have seen the one on eBay, but it looks to be a B-stamp.
     
  2. kiffsta

    kiffsta Senior Member

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  3. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Im guessing there will be one somewhere in the abyss known as the parts bin .... Ill get back to you :D
     
  4. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    @Grasshopper should be a crank or two with rods under the house somewhere.
     
  5. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Somewhere ... :lolsign: ... u obviously havnt seen 'under the house' lately :help:
     
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  6. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Bit hard when I'm 500kms away lol :oops:
     
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  7. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Ill get one from that tub with the engine u dismantled at TAFE
     
  8. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    I think I already put the crank & rods from that into the 3LN6.
     
  9. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    And the ones u took out are 'under the house' ? :commando:
     
  10. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Yep.

    There's also the 3LN7 motor with the head & barrels off sitting there
     
  11. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Which motor was in that bike originally?
     
  12. Xavier492

    Xavier492 Member Premium Member Contributing Member

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    I got another B-stamp one and I'm *hoping* the shorter conrods cause no issues.
    I am also hoping it will act like a stroker kit for the inner 2 chambers... unless anyone has any objections.
     
  13. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    I don’t think having 2 Conrods that are slightly shorter would be a good thing.... the pistons to suit those rods will be different and if you get it all wrong in the mix and match the result would be catastrophic.
    Not to mention the dynamic balance would be out and given the rpm these engines operate at it really wouldn’t be good.....

    Conrod length doesn’t affect the stroke, the crank determines the stroke while the Conrad length and piston height ( from the gudgeon pin ) is more about getting compression ratio right.
     
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  14. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I don't think it'll work too well, you'll lose a lot of compression from the middle 2x cylinder's
    Also have you compared the weight of the 2KR and 3LN conrod's if the 2KR rod's are 2mm shorter then the 2KR might have a lighter conrod which will cause balance drama's.
    There was mention of 2KR / 3LN conrod's has been discussed here
    https://2fiftycc.com/index.php?threads/3ln-2kr-interchangeability.9452/


    How much is your kidney worth ?
    https://www.ebay.com.au/itm/YAMAHA-...685111?hash=item41e8449d77:g:d9cAAOSwdRparu8y

    Although this one look's to be the same one, or they used the same picture ?
    $53AU plus post
    https://www.nanronline.top/index.php?main_page=product_info&products_id=4937


    There is a good used set of rod's for sale in Russia for $100AU ea too
    http://www.motosale.ru/product_3660.html
     
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  15. Xavier492

    Xavier492 Member Premium Member Contributing Member

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    Alright, thanks !

    Back on the hunt if anyone has a 3LN conrod they can spare.
    I didn't measure exactly how shorter the 1HX rods are, but they weigh 2-3g lighter than the 3LN rods.

    The eBay/other listing are the same - I saw it listed in Yahoo. I'm not 100% certain but the stamp looks like it says B.

    Now I know the part number, I can check if my local Yamaha workshop can find parts - if no one here has any.

    @Linkin I will NEVER use aliexpress parts again. Absolute rubbish. I tried to install the AHL pistons yesterday and they got scratched when I put the piston rings in and 2 got chipped when I put the chambers in place - made of some weak metal. Not only that, I wouldn't be in this position if it weren't for aliexpress gaskets failing.
     
  16. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    The issue is the rod length to stroke ratio. It has nothing to do with compression etc. For a high revving engine you want a longer rod. This is from the factory manual supplement for the 3LN1 and I guess it says they lengthened the rod by 2mm. That is a 2.3 ratio and I don't recall seeing one that high before. In the '90s people used to fit 600cc+ engines to 250 GP race bikes and use them for singles class racing. As usual the trend was for more and more displacement. I did an engine for one of these things and went for low displacement higher rpm. Was a headache to lengthen the rod by such a large amount but it was a winner.
    FZR_Rods.jpg
     
  17. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    But if you use the Piston from the longer rod.. with a shorter rod.. then the overall height will be 2mm shorter and a lot less compression.
    I am sure you will find the wrist pin to crown height on the 2 will be different.. most likely by 2mm :)
     
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  18. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    The blue/white virgin fizzer I bought

    I find that really strange... perhaps you got a dud set... I've always said their gaskets are no good though.

    Installing pistons/rings is a finicky job, it doesn't take much to stretch/bend a ring or scratch a piston.

    When you were fitting the cylinders, did you try to do all 4 at once? It is extremely difficult if not impossible. I put the middle pistons on TDC and fitted those first, rotated the crank while pushing the cylinders down further, until I could get the outer 2 in.
     
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  19. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Sorry, I meant the issue as to why rods are different length. For all of the reasons that Andy and others have already stated, using different length rods is not worth considering..
     
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  20. Xavier492

    Xavier492 Member Premium Member Contributing Member

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    I tried doing them by connecting to the conrods first then slotting the chambers over them while compressing the rings.
    My #4 cylinder was seized because of the bent oil ring. Now I have to get that chamber re-honed.

    I think now I will slot the pistons into the chambers first and then try to line up the small end with the pin.

    I mentioned before that one of the AHL pistons got chipped when the chamber sat on it while I was working on another piston, so out came the dremel to get the top smooth again.
     

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