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Help FZR250 - coolant leak in hardline behind block/head

Discussion in 'Yamaha 250cc In-Line 4's' started by skylinerd1, May 4, 2019.

  1. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    If your going to reuse that rod then get it closed and honed back to the original size so you have the correct 'crush' on the bearing shells.
     
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  2. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Here from the FZR400 1WG. If you look at the 250 manual you can see similar. Obviously the 250 manual needs to be translated. On this rod the 'E' means nothing. Probably like the 'C' on yours.

    Crank_0.jpg
    Crank_1.jpg
    Crank_2.jpg
     
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  3. skylinerd1

    skylinerd1 Member Premium Member Contributing Member

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    OK whats the best method to remove the timing wheel/flywheel as it looks to me thats got to come off to split the crankcase halfs? I have removed the bolt for that and the gear at the opposite end of the crank. Looks to me like I have to remove the flywheel either way as I see bolts going through the lower and upper halfs of the crankcase. And I imagine any machinist will want it gone to do his thing polishing this journal if its possible.

    I might need to custom make a puller out of my T puller?

    I think that rod thats tight on the crank is off the earlier motors pre 3ln1. Thats why its tight its actually almost crushing the bearing onto the crank journal.
     
  4. skylinerd1

    skylinerd1 Member Premium Member Contributing Member

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    Now that I look at the flywheel again the keyed boss that holds it on has a massive thread in it compared to the nut that actually holds it on but inside it tappers into where the retainer bolt screws in... I think If I find a bolt that matches that big thread and machine a tapper on that in my lathe and recess the end of it a touch so it cant damage anything that might work.

    I assume there is a proper hardened tool for this job?
     
    Last edited: Jun 30, 2019
  5. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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  6. skylinerd1

    skylinerd1 Member Premium Member Contributing Member

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    Ok thats where I went wrong I tried with a normal bolt (grade 10.9) though. It had a tapper on the end of it already so I figured give it a go. Nope.

    I will go get a nice high quality cap screw and try that.
    I think it deff needs something down in the hole to take the load (will allow the big bolt to turn and not work against itself in that taper) as suggested in your ^^ post.
     
  7. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    For the load bearing screw I used as long I could possibly go.
     
  8. skylinerd1

    skylinerd1 Member Premium Member Contributing Member

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    Yep it takes a surprising amount of force to move that thing for what is....
     
  9. skylinerd1

    skylinerd1 Member Premium Member Contributing Member

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    Ok got that apart the mains look fine to me all things considered.

    Anyway I dropped it off to a machine shop to see if they can polish that rod journal and get one of those rods sized to fit.

    They mentioned the crank might not be able to do it because of their tooling sizes which is fair enough. I might have to try Tauranga if these guys here in Rotorua cant do it.

    I need to provide them with the relevant fzr400rr and fzr250rr pages which I have found so I'll go print them out tomorrow.
    I see oversize bearings on alibaba I guess I can just go through alibaba find what oversize sizes there actually are and just let them know whats available?

    Stick with AHL branded ones again? I see +25 through to +150? Anybody had experience with this??
    https://www.aliexpress.com/item/32281393624.html

    I just want to give these machinists as much info as possible on whats available when I go back there. Standard size mains shouldnt be an issue its just these rod journals and the rods themselves as one cyl will certainly have to be worked on.
     
  10. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    To the best of my knowledge these cranks are not designed to be ground undersize. Expect that they might break if you do so.
     
  11. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    @Linkin has experience with doing a full rebuild with AHL bearings, IIRC he got all of the tolerances in spec by doing some mixing and matching, there is a post on here somewhere where he gives details - hopefully he can chime in

    But the reason I am mentioning this is because it may be preferable to get the bearing shells first, then have any work done to match the size(s) of those shells

     
  12. skylinerd1

    skylinerd1 Member Premium Member Contributing Member

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    That is what im doing. I went around all the local shops here in Rotorua none of them even had a stone small enough to grind these tiny journals. (need a stone to suit about 14-16mm wide journals). None of them filled me with confidence that they had any experience with these either so I was kinda thankful for that. Rotorua being a logging town these guys are doing BIG stuff nobody here or even within 100kms has a crankshaft grinding machine small enough to do this.

    Anyway theres an outfit down in CHCH that reckon they can do it and they are experienced with FZR400R so im going to send it to them with a set of .25 under size bearings.

    I keep looking at the damage and im half tempted to put some acid on it to burn the alloy particles out of it and then polish it by hand that's the only way I can see it staying the same 27mm diameter as it is now. These guys in chch reckon taking .25mm out of each rod journal is ok.

    The other outfit that said they could most likely do it (they actually have custom made their own cranks for bikes here in NZ) was down in wanganui apparently they are the goto for the local bike shops here in Rotorua.
     
    Last edited: Jul 7, 2019
  13. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    For what it's worth you may be able to remove the alloy particles if they protrude slightly above the surface with a paint scraper - shortened and used around the circumference of the journal

    I've seen some ingenious polishing of a journal on youtube with emery fabric and of all things a shoelace wrapped multiple times and cycled back and forth - it seemed to achieve exactly what the polishing machines did with a little bit of effort A.K.A. elbow grease
     
  14. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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