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Thread: Tf 125 motor bucket thingy

  1. #1
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    1st June 2014 - 21:23
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    Tf 125 motor bucket thingy

    Well, I thought it would be a good idea to tear Into this motor while I am stuck at home, was just going to check top end but the left hand main bearing didn't feel right so split the cases found rust on the bearing and putting where the oil seal sits. I got the motor in unknown condition no wonder it wouldn't idle.. looks like it's been sucking air and running lean... it has rooted the top end also anyone for ideas on what to do

    Lost cause or?...

    I am thinking of polishing crank end and adding a washer to space the oil seal out throw new main bearings in new small end bearing and piston with a rebore.
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  2. #2
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    1st June 2014 - 21:23
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    Turned crank in the lathe slowly with some 2000 grit paper and this is the result, does anybody have a workshop manu for a tf/ts 125 motor? I can't seem to find one
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  3. #3
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    18th May 2007 - 20:23
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    .
    You might be able to polish that oil seal surface on the crank up some more. Usually the mag side bearing is a tight fit on the crank. But the hot trick is to polish the crank until a new bearing is just a slip fit. this does away with any power robbing side loading as the engine heats up and the cases expand. It does not matter much that the crank spins inside the bearing. A race engine is not going to do the hours of service that a road/farm bike does.

  4. #4
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    I see some decent engineering machinery in the background.

    If you are into a bit of two stroke tuning page 2000 on the ESE thread is worth a look. https://www.kiwibiker.co.nz/forums/s...tuner/page2000

  5. #5
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    Quote Originally Posted by TZ350 View Post
    .
    You might be able to polish that oil seal surface on the crank up some more. Usually the mag side bearing is a tight fit on the crank. But the hot trick is to polish the crank until a new bearing is just a slip fit. this does away with any power robbing side loading as the engine heats up and the cases expand. It does not matter much that the crank spins inside the bearing. A race engine is not going to do the hours of service that a road/farm bike does.
    Ah, nice that sounds like a plan. I read on one of the other posts about pressing some slugs Into the crank for vibration I plan to up the rpms did you press the slugs into the big holes or smaller ones?
    What's the best thing to do with the bore, and piston? Go for something like a rg500 piston like others have done or keep it simple? Bore or buy a new cylinder?

    I am just getting into 2 stroke engines so I will have many questions but will start on that thread, thanks.

    Yep.. good ol little myford the drill press makes it look tiny... I haven't actually used it much since getting a bigger harrison lathe but still nice to use for smaller bits.

  6. #6
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    12th February 2004 - 10:29
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    You need to measure the bore. A quick hone and a new piston may be all it needs. Bearings are dirt cheap from your local bearing shop and you may be able to get new seals there as well. Ask about "seal savers". These are nothing to do with Greenpeace but very thin sleeves that are slid onto shafts over where the seals run. A slug of aluminium goes in the big hole on each crank wheel. If you have it all apart and the bearings you can see aren't good there may also be damage on the big end bearing as well. It may be worth giving it a go but if it fails and you are really unlucky it could send bits of cage up the bore and into the cylinder. A crank rebuild might be worth doing depending on what you want to achieve.

    The slugs of aluminium worked really well for me. Others seem to have had less spectacular results.

  7. #7
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    1st June 2014 - 21:23
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    I did think about a speedi sleeve, I'll see what happens with a slip fit on the bearing.

    The bore measures 56.20mm

    I made a quick jig for the crank shaft works quite well actually.. I do have a granite surface plate but missing the tooling may be a good excuse to buy some bits and pieces. I am looking forward to rebuilding this engine as it's the first time I have tried something like this, lots to learn.

    I seem to of misplaced my 50-75 mm micrometer so was measured with a telescope gauge and a digital caliper not idealClick image for larger version. 

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  8. #8
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    12th February 2004 - 10:29
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    Nice little jig. With a few more bits you will be able to check the balance factor as well. It's real easy.

  9. #9
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    18th May 2007 - 20:23
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    Use the Google "site:" search term to find all the posts about "balance factor" and how to check it posted on the ESE thread.

    Copy and paste this line into your Google search bar:-

    balance factor site:https://www.kiwibiker.co.nz/forums/s...s-engine-tuner

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  10. #10
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    Cool, looks easy enough to balance it using this stand, the boy and I where bored today so made a engine stand.. there isnt much I can do until shops are open again so filling time in
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  11. #11
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    2nd July 2013 - 11:52
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    I'm going to have another go at a tf engine
    I have a heap of 1981 cr125 pistons at that 56mm range
    i'm over buckets

  12. #12
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    1st June 2014 - 21:23
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    Quote Originally Posted by mr bucketracer View Post
    I'm going to have another go at a tf engine
    I have a heap of 1981 cr125 pistons at that 56mm range
    What size are they, and what rod size? Want to part with a few if they will work? I am looking to upgrade similar to what F5 Dave has done at the TF engine he built.

  13. #13
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    20th January 2010 - 14:41
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    Quote Originally Posted by layton View Post
    What size are they, and what rod size? Want to part with a few if they will work? I am looking to upgrade similar to what F5 Dave has done at the TF engine he built.
    I thhave a heap of Cr125M pistons her in various sizes 56mm and up they are 14mm pins
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  14. #14
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    At nice, perfect saves changing the rod.

    The TF piston measures approx 66.50 mm dome to skirt and 56mm across

    What's a cr piston in comparison

  15. #15
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    20th January 2010 - 14:41
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    Sorry replied as a PM
    about 59mm to edge of piston 61 or 62 if top of crown
    pined at 5 and 7 oclock
    center of pin to edge of crown 28.5mm
    But dont those Suzukis have a 19mm big end pin i would get rid of that and replace with a 20mm pin.

    later ones like pro X will be thinner single rings and likely more available and lighter
    http://www.pro-x.com/wp-content/uplo.../2015_TECH.pdf
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

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