Help FZR250 Rebuild but cant source conrod bolts?

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

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  1. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Looking at the shank type on the OEM Yamaha conrod bolts with the machined shaft and spiral groove I reckon they were supposed to be interference fit originally but aren't.

    The Kawasaki bolts are a beautiful fit, I'll take photos today to show the differences
     
    ruckusman, Nov 6, 2022
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  2. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    A promised here's some photos of the rod bolts installed in a conrod for comparison


    Note the FZR250 rod bolt has material which overhangs the top [outer] edge of the rod cap, whereas the ZXR250 doesn't have any excess material overhanging the rod cap
    IMG20221106193308.jpg

    IMG20221106193356.jpg
     
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    ruckusman, Nov 8, 2022
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  3. jmw76

    jmw76 Well-Known Member

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    Do the bolts go in that way? On most engines I have worked on the bolts come in from the conrod end and nuts go on the cap end. Access to the nuts from the top could be difficult/impossible when the nuts are on the top when the rods are installed in the motor.
    Where the bolts are inserted from the bottom, the rods usually are threaded to accept the bolts without nuts.
     
    jmw76, Nov 8, 2022
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  4. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    rodbolts.jpg
     
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    maelstrom, Nov 8, 2022
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  5. jmw76

    jmw76 Well-Known Member

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    Well there you go. You learn something every day.
     
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    jmw76, Nov 8, 2022
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  6. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Sorry, I have shown up late for the party again...

    The ZXR bolts are TTY and you need to read the ZXR manual as there are a number of different tightening options depending on what you're doing e.g. reusing bearings; new bearings; new conrod etc. Apologies if this has been discussed already.
     
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    Frankster, Nov 8, 2022
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  7. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    UMM, we may have but I do no recall it being discussed in respect of these bolts, that's an excellent tip - thank you
     
    ruckusman, Nov 8, 2022
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  8. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK, on the weight issue between the bolts, I've measured one of each of the FZR250 -v- ZXR250 bolts

    ZXR250 bolt - 10.07 grams
    ZXR250 nut - 2.60 grams
    ZXR250 nut and bolt - 12.67 grams
    FZR250 bolt - 9.79 grams
    FZR250 nut - 2.73 grams
    FZR250 nut and bolt - 12.55
    I did this on my newly acquired 0.01 gram accurate scales because I just received a package from the Transvaal
     
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    ruckusman, Nov 8, 2022
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