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

Help FZR250 Rebuild but cant source conrod bolts?

Discussion in 'Yamaha 250cc In-Line 4's' started by ironmonkey, Jun 6, 2021.

  1. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    BTW - I'll measure some 6mm drills that I've got and see if I can check the reamed portion of the OEM rods, I know it's larger than 5.98mm which is the diameter of the shank of the OEM bolts - I have very slight movement on the bolts on the rod which I have here
     
  2. ironmonkey

    ironmonkey Active Member

    Messages:
    21
    Likes Received:
    7
    Trophy Points:
    173
    Joined:
    Jun 12, 2020
    Location:
    australia
    My Bike:
    fzr250
    While the bolts can turn alittle, we are talking about a completely different shape. The shape of the Kawasaki bolt is a rounded rectangle, while the FZR250 bolt (its literally in front of me on the computer desk) is much more of an oval shape.

    If the bolt head is of the same lower dimension, it will require removing a substantial amount of material.

    The diagram provided doesnt appear to show the lower dimension of the kawasaki bolt head - can someone confirm?
     
  3. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

    Messages:
    5,102
    Likes Received:
    3,472
    Trophy Points:
    1,148
    Joined:
    Dec 23, 2012
    Gender:
    Male
    Location:
    Thailand
    Home Page:
    My Bike:
    Yamaha FZR400 3TJ1, Honda MC22
    "Someone"? You mean me. I bought the bolt from Impex 3.51 USD, and I made the drawing. I do things like that to help other people on the forum. You're welcome.

    The unchamfered section of the bolt head is 2mm thick. So what if the Kawasaki bolt head is not exactly the same shape? It has more material and could easily be ground to shape by hand to fit the Yamaha rod if needed. It is obviously an easy fix to this issue.
     
    • Like Like x 2
    • Agree Agree x 1
  4. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    I agree there is no problem here - OEM bolts are NLA, Honda bolts are NLA, no other solutions are available - this is an excellent solution IMO

    These bolts are the appropriate quality, length, shank diameter and might need a tiny bit of material removed either from the bolt head recess machined into the rods, or alternatively a tiny amount of material removed from the bolt head - if that is necessary at all

    huge kudos to @maelstrom for getting that bolt and doing the awesome measurements and drawings

    With the other bearing shell solutions from Suzuki, Honda and Kawasaki the entire crank and conrod can be rebuilt with OEM quality parts to OEM spec
     
  5. ironmonkey

    ironmonkey Active Member

    Messages:
    21
    Likes Received:
    7
    Trophy Points:
    173
    Joined:
    Jun 12, 2020
    Location:
    australia
    My Bike:
    fzr250
    When I said someone I meant either you and ruckus (who presumably has also ordered the bolt).
    And sorry didnt know you actually did the drawing. Thanks.

    I know grinding it can potentially heat it up and change its properties. Just covering my bases. I'm not an expert on these things so I'll defer to people who know better. If its a tiny amount of material its a non issue but the bolt head is a completely different shape; thats not tiny in my book (particularly small parts that absorb less heat without getting hot) so just making sure.
     
  6. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    I wouldn't grind the bolt head, I would get them and then remove the material from the edge of the rod, if any material needs to be removed, it will be tiny and can probably be fine with just a sharp file on the very edge

    Have you looked closely at one of the conrods?
    When you do you'll see where I'm talking about

    Also, whenever I'm removing material and don't want to incur heat damage, Ive got a variable speed 5" grinder polisher and use it on lowish speed with a flap disc, never remaining in the one spot , they're a great invention

    Flap disc would work for bolt heads, but is overkill in this instance
     
  7. ironmonkey

    ironmonkey Active Member

    Messages:
    21
    Likes Received:
    7
    Trophy Points:
    173
    Joined:
    Jun 12, 2020
    Location:
    australia
    My Bike:
    fzr250
    Ah right, I see what you mean. I kept thinking I should grind the bolt head, not the rod itself.

    Im on the verge of giving up so if this kawasaki solution actually works it would be awesome.

    Also, you mentioned there are also other bearing shell solutions - just curious which ones (is there a thread on this too?). I have a set of AHL bearings but their tolerances are apparently on the worn side accroding to a thread here.

    May as well do them as well while my engines are apart.
     
  8. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    Yeah I wondered if you were looking at a rod - the edge which may have to be modified is a tiny amount, I was going to use a file to do it gently.

    Tell me about your AHL shells?
    What sort of accuracy are you able to measure to?

    There should be numbers stamped on your engine case(s) which give some numbers, from those we can work out:
    main journal bore diameters in the cases
    main journal diameters

    conrod big end bore diameters
    big end journal diameters

    AND which shells were installed by Yamaha AND their thicknesses

    That's where the bearing shell thicknesses come in - they are marked by colour AND part number and each successive shell differs by 1/100th millimetre

    I went on an absolute research binge and just threw down links to the various alternative options in shells - I need to go back and sort through the mess - but a solution is available

    Honda, Suzuki and Kawasaki all have parts which are suitable AND they give their thickness ranges of their shells

    Once I have my engine apart I intend to measure everything

    Don't give up now - I've done a **** load of research in recent weeks to make this process as smooth and simple as possible

    ALso let me know if you want to do a joint order for the various bits to share shipping costs - impex is about $25USD for just the bolts which bumps the price, but they do deliver in a quick time frame
    \
    Every Kawasaki dealer's website here that I check here comes up as NLA on the bolts, which is BS
     
    • Like Like x 1
  9. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

    Messages:
    4,289
    Likes Received:
    2,504
    Trophy Points:
    918
    Joined:
    Oct 6, 2016
    Gender:
    Male
    Location:
    Albury 2641
    My Bike:
    1987 Yamaha SRX250, Honda 1974 SL125 K1, 2022 Triumph Tiger Sport 660
    I would be a bit circumspect on removing any material from the conrods... you would really need to check all the weights and as a minimum ensure they all remained within the same weight difference.
    Remember.... these things run to 18,000 plus and the rotating elements are finely balanced.
    If it was going to be done I would defer to an engine specialist that knew his stuff with small displacement ultra high revving Japanese engines... Just my 2 cents worth.
     
  10. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    Understood - I'll take a picture with a decent camera so you can see where I mean - you'd be hard pressed to measure it in 0.01 gram accurate scales it's such a tiny amount
     
  11. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    I just re-measured this and noticed an error - the width is 13.5mm
    IMG20211115132802-width.jpg

    Here is a photo with the depth of cut of the recess for the bolt head - notice that the hole isn't centred as it's towards the edge of the conrod, also the Kawasaki conrod bolt head is 9.84mm across the short axis

    Here's a pic @maelstrom just sent me

    bolt.jpg

    I'd be astonished if they don't go straight on - the photograph of the Kawasaki bolt head is slightly deceptive

    FZR250 bolt heads are 13.98mm wide, there's the outer edges that go over the end of the rod which essentially hang there doing nothing

    ZXR250 bolt heads are 12.84mm wide and at the 13.5mm point which is where the conrod machining would have potentially fouled the bolt head, the Kawasaki bolts are not that wide
     
    • Like Like x 1
    • Informative Informative x 1
    Last edited: Nov 16, 2021
  12. ironmonkey

    ironmonkey Active Member

    Messages:
    21
    Likes Received:
    7
    Trophy Points:
    173
    Joined:
    Jun 12, 2020
    Location:
    australia
    My Bike:
    fzr250
    Below is my understanding of whats its going to look like. As per your measurements the yellow shape is slightly wider than the 12.5mm line you drawn. I just dont see this going straight on unless the width of the bolt head is substantially smaller.

    It looks like getting that curvature on the rod itself will be a pain (a very small dremel) and its better to grind the bolt head. Especially when someone rightfully pointed out, working on the rod risks unbalancing the assembly.

    I guess if this is our best option im happy to go for the ride...

    upload_2021-11-15_21-8-13.png


    As for the AHL bearings - I dont trust my technique using the plastiguage, especially big end bearings. I found it really hard to assemble conrods without moving the assembly as least abit, which of course risks smearing the plasticguage.

    Relying on someone else's measurements here: https://2fiftycc.com/index.php?thre...nformation-clearances-etc-fzr250r-3ln1.11237/
     

    Attached Files:

    • Like Like x 1
  13. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    Can you find the numbers which should be scribed on your engine cases?
    There should also be a set of number on your crankshaft LHS and there are stamped in ink numbers on the side of each conrod also

    There should also be remanants of paint colours on the shells themselves, hopefully you kept them with their respective locations
    I'll try find the post which details the above with respect of the FZR400 manual - the process is identical
     
  14. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    Read the few posts here

    https://www.2fiftycc.com/index.php?threads/fzr-250-overbore-300.10253/page-2#post-124506

    Let's get the numbers for your cases, crankshaft and conrods as a first step

    This also has the process of determining the shells colours- only thing to know is that the numbers on the engines case, crankshaft and conrods correspond to actual sizes -

    https://www.2fiftycc.com/index.php?...acially-slow-project.3099/page-14#post-134373

    I've got a zeal engine with the cases split already, tomorrow I will measure the cases, crankshaft mains and big end journals and conrod sizes and give those numbers actual sizes - been meaning to do that anyway

    Then it becomes a matter of measuring the shell material thickness with a dial indicator
     
    • Like Like x 1
    Last edited: Nov 15, 2021
  15. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    @maelstrom had already done an accurate measurement of the bolt head, it is from the diagram 9.94mm


    I just measured an FZR250 conrod bolt on the short axis also, it is 10.75mm
     
    • Like Like x 1
  16. ironmonkey

    ironmonkey Active Member

    Messages:
    21
    Likes Received:
    7
    Trophy Points:
    173
    Joined:
    Jun 12, 2020
    Location:
    australia
    My Bike:
    fzr250
    ok, getting back to this. If you are happy to organise a joint order, l can paypal you. But then you'll need to ship my order to my address (im in sydney), so we only save $12 each excluding your time to ship my order as well. Maybe from your POV its not worth it, but let me know
     
    • Like Like x 1
  17. ironmonkey

    ironmonkey Active Member

    Messages:
    21
    Likes Received:
    7
    Trophy Points:
    173
    Joined:
    Jun 12, 2020
    Location:
    australia
    My Bike:
    fzr250
    I should give a heads up after finally get back to this. The kawasaki bolts do not fit. They wont slide into the conrods, ie slightly too wide.

    Thats well and truely the end of my part finding adventures here.

    The nuts are compatible though.
     
  18. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    Have the rods reamed to fit the bolt shafts.

    I wasn't overly impressed with the fit of the OEM Yamaha bolts into the rods, some of mine were tights from poor machining - I could see it through a loupe and others were sloppy by comparison.

    BTW I have a set coming which will reach me in coming weeks, give it three, then I'll measure them precisely, it will need 0.01 - 0.03 material to be removed by reaming is my guesstimate
     
    • Like Like x 1
    • Agree Agree x 1
    Last edited: Jun 25, 2022
  19. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,416
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    Much later than anticipated but my Kawasaki ZXR250 conrod bolts arrived and they are a perfect fit.

    Took three light taps with a piece of brass rod that I keep for just such occasions and the interference fit into the conrod caps was perfect.

    No need to remove any material whatsoever and the upper portion of the conrod is a perfect registration fit with no slop

    The ZXR250 bolts are a better fit than the OEM Yamaha ones IMO.

    Huge shout out to @maelstrom for helping to sort this out
     
    • Winner Winner x 3
    • Like Like x 1
  20. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

    Messages:
    5,102
    Likes Received:
    3,472
    Trophy Points:
    1,148
    Joined:
    Dec 23, 2012
    Gender:
    Male
    Location:
    Thailand
    Home Page:
    My Bike:
    Yamaha FZR400 3TJ1, Honda MC22
    and therein lies the problem. They are not meant to "slide" in.
     
    • Agree Agree x 1
    • Informative Informative x 1

Share This Page