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Help FZR250 Rebuild but cant source conrod bolts?

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

  1. thebeefsalad

    thebeefsalad Well-Known Member Premium Member

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    used MC22 conrod bolts measured with cheap calipers

    outer threaded diameter = 5.85
    shank diam=5.97
    shorter diam of bolt head = 10.19 <-- did my best without pressing one out, definately smaller than 10.7 per my calipers
    longer diam of bolt head = 12.84
    OAL=41.6
     
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    Last edited: Jun 9, 2021
  2. Gen

    Gen Well-Known Member

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    I have zilch MC22 stuff
     
  3. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    I think just buy one of each bolt and nut Honda, Suzuki & Kawasaki then make the decision.
     
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  4. gregt

    gregt Well-Known Member Premium Member

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    As I said earlier, the CBR range is worth looking at. The early 600 and the 400 use 6mm bolts as do the VF400F and some other 400 V4's.
     
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  5. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    I looked for the Suzuki bolt - I could be wrong, but it looks to screw into the conrod upper directly - don't quote me though

    EDIT - here's the parts diagram for the GSF250V
    http://www.mickhone.com.au/partFinder/fiche/suzuki/2000/gsf250v/crankshaft
    That bolt looks to screw directly into the top of the conrod

    bolt part number is 12163-06C00 - so I'd say skip that one

    ZXR would be definitely worth investigating further - fellas @Linkin or @Frankster or anyone else got any knowledge to share with respect to the ZXR250 conrod bolts?
     
    Last edited: Jun 9, 2021
  6. Murdo

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

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    Please, just reuse the old bolts and put us all out of our misery.
     
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  7. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    I'm inclined to agree however as @maelstrom and I are AHEM "planning" an overbore build [still] well definitely need new rod bolts, and this is for the collective benefit of all.

    We've also pondering if big end shells and crank journal shells might cross over from the other similar bikes in other brands might work, because almost everything Yamaha is NLA which just SUX
     
  8. ironmonkey

    ironmonkey Member

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    OAL of the FZR250 is about 40.

    With the slightly smaller bolt head and everything else being right, should these fit the bill? Can an engine expert chime in please.


    Where do I source nuts? Buy the ones for a 6mm bolt like the MC22 or can i go to find one in the hardware store? No idea these were even more critical.
     
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  9. gregt

    gregt Well-Known Member Premium Member

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    6mm nuts from a similar application will work. So the Honda ones will work. They're made to a higher spec and closer tolerances than normal over the counter rubbish.

    A bolt a little longer won't hurt. But does no-one own a micrometer ?
    Calipers are not accurate enough for shank measurement as the fit is critical.
     
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  10. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    I've got a micrometer, many actually and a partially disassembled Zeal engine in the garage, I can make those measurements, BUT you should see my garage, you just about need to be a mountaineer to get in there - I have a serious problem...

    I will deal with that part of the equation then order a Honda bolt
     

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