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Help Honda VT250F Connecting Rod Bearings

Discussion in 'Your 250cc Projects' started by Getzie, May 9, 2024.

  1. Getzie

    Getzie Member Premium Member

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    Hey Guys,

    I've recently started the project of tearing down and completely rebuilding a Honda VT250F. Hoping to restore it from not running and turning to junk to a beautiful bike again.
    However the biggest issue I am running into is parts.
    Right now I am stuck trying to figure out the bearings for between the piston connecting rods and crank shaft. The measurements I am getting for the crank shaft are outside of what the service manual is suggesting they should be and the rods and the same.
    So the actual questions, how close of a fit up do the bearings need to be, and is there anywhere other that cmsnl that I can source the bearings from. I need to replace all four bearings and don't really want to spend $20 per bearing if I can avoid it.
    Any and all help is welcome.
    Thanks
     
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    Getzie, May 9, 2024
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  2. Frankster

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

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    Hi Getzie, Welcome to the forum. From my experience, the VT250F motor (MC08) is pretty much a standalone engine and doesn't share many parts with other Honda engines that followed it or those that 'look' like a derivative of it e.g. VF400F, VT500F etc. I have never rebuilt a bottom end on a VT250F, but I know that is probably their greatest weakness. Damage to the crank, crank bearings and big-end bearings is common on bikes that have been ridden hard or not serviced properly. There was an issue with the PRV that also added to oil starvation related problems. I have attached a PDF document for you regarding the crankshaft/big end issue. I'd probably buy those CMSNL bearing shells and have the crank done if you're keen on doing a full resto. The VT250F also has a crap Reg/Rec. @Murdo restored a VT250F a few years back. He had the bores done and a few other items, so he might be able to point you in the right direction. I think his build is on this forum somewhere. Good luck with your build. Frank
     

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    Frankster, May 9, 2024
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  3. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    ruckusman, May 9, 2024
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  4. gregt

    gregt Well-Known Member Premium Member

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    You ask how close a fit the big ends should be.
    Aim for 1.5 - 1.6 thou. that is .0015in to .0016in clearance.
    Plastigage is probably the easiest way to measure this.
    i don't know where Melton is but Plastigage is available from places like Repco in Australia
    and similar auto parts suppliers elsewhere.

    While the crank is apart it's worth looking at the edges of the oil holes where they break out onto the bearing
    surface. Any sharp edges should be removed. Honda didn't finish cranks well around this period.
     
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    gregt, May 10, 2024
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  5. Murdo

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

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    Murdo, May 10, 2024
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  6. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Hot damn you've got both gurus onboard - you're in safe hands now.
     
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    ruckusman, May 10, 2024
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  7. Getzie

    Getzie Member Premium Member

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    Thank you guys for the info, looks like I have a bit of reading and more learning to do.

    Honestly at the moment I have been measuring the smaller parts with a micrometre but that only goes up to 2.5cm, larger parts I have been using a broken set of callipers and cross referencing on a ruler, however I intend to get a new set up working and accurate callipers when I can.

    I'll get some images up eventually of the bike, befores, durings ect. but lets just say the bike was $200 from ebay and was listed as for parts. So it needs a LOT of work. Good thing this is a hobby and not a job :D
     
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    Getzie, May 11, 2024
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