USD Fork swap.....what should i make this bushing out of????

Discussion in 'Some Assembly Required' started by MILLENNIUM FALCON, May 21, 2013.

  1. MILLENNIUM FALCON

    MILLENNIUM FALCON Been here awhile

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    I am swapping to USD forks and the closest bearing I can find has a 2mm larger inside diameter than the triple tree stem. So i will need to make a bushing to press onto the stem to fit the new bearing. The bushings will be about 17mm in length, (i.d)28mm (o.d) 30mm. I'm just looking for some insight on materials for this bushing. Thank you
    #1
  2. MrPulldown

    MrPulldown Long timer

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    Have you considered using your steer stem. Press it out of you stock triple and into the triple of the USD forks. THsi is the way I got mine to fit. If the length is good it should work out. I did need to shave and shim here or there. I was lucky and the bottom of the stem of the two forks where the same size. I have seen people make spacers for the bottom fo the stem.

    If you are set on making a spacer for the bearing, I would use some kind of steel. What type; I don't know? Getting the interferance fit right could be tricky.
    #2
  3. Luke

    Luke GPoET&P

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    Myself I'd use aluminum. Soft, but easier to machine accurately.

    However, a 1mm wall bushing is thinner than I could make accurately because it would flex when pushing the lathe bit into it. The wall thickness will need to be within 0.1mm total to get a decent press fit. I'd use a smaller bearing and make a bushing with a thicker wall. 2mm minimum.

    YMMV, depending on operator skill.

    What size bearing do you need? There may be other options.
    #3
  4. sailah

    sailah Lampin' it

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    It's going to be pretty tough to machine and press a spacer that big with a 1mm wall diameter. Not saying it can't be done but not your average lathe job being the material has zippo for strength at that point.

    How about some 1mm shim stock cut with tin snips? Form it around a steel rod and it should be easy to get that in the bearing then onto the stem.

    Or as suggested above, use the existing stem. I did a modified version of both on my latest bike and made a new stem out of 6061 aluminum. The piece of aluminum was $10 and took a couple hours of fitting. The most expensive part of the operation was the M20 tap for the threads on the top where the KTM nut went and even that was only $25.

    Post up some pics and measurements and maybe it'll help the creative juices flow.
    #4
  5. MILLENNIUM FALCON

    MILLENNIUM FALCON Been here awhile

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    Thank you for all the replies and good advice. I will try to post some pictures and specs. as I did into things more. I thought about making a new stem, but I really think I can make these bushings and if all goes well it should be a piece of cake. Ill keep you updated. Thanks again. I appreciate any and all comments.
    #5
  6. Lesharoturbo

    Lesharoturbo Nerdly Adventurer

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    I am not sure aluminum would be a good idea. With it between the hardened metals of the stem and the bearing, it would be like gum and wear very easily. Also, there may be some galvanic corrosion if there were any moisture in the void around the stem. This may also increase the wear as the aluminum turns to powder.

    The best idea is to find a donor stem that will mate the two together.
    #6
  7. Beezer

    Beezer Long timer Supporter

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    I've done a couple like that.... the easy way is to press out the original stem & fit it to the new bottom triple. braze, flame spray, or weld the stem to fatten it up, then lathe it to the size of the hole in the new bottom. the top bearing can be the oem. the top triple gets shimmed by cutting off a piece of the donor stem & drilling it out to the size of the original stem. (the od is already right for the new top). actually, leave the piece long while in the lathe & cut it after it is on size
    #7
  8. MILLENNIUM FALCON

    MILLENNIUM FALCON Been here awhile

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    That would work. The only problem I can see is that I would have to bore out the triple clamps because both the top and the bottom clamp have 28mm holes in them (the dia. of the inner race of the bearings.) If I fatten up the shaft to 30mm or get a new stem I will have to modify the clamps to make it work. I made some test bushings tonight. I figure.....since my bearings will get here tomorrow I might as well try it and see if it works. If it gives me trouble I will be looking for a new set of clamps/Stem. The forks I have will work with lots of different clamps and they are the expensive part.
    #8
  9. Beezer

    Beezer Long timer Supporter

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    the original stem is larger diameter than the one in the new USDs? wow... backwards from the ones I have done.
    #9
  10. MILLENNIUM FALCON

    MILLENNIUM FALCON Been here awhile

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    Yeah I found that strange as well. The origional uses a large bearing on the bottom and a tiny bearing on the top.
    #10
  11. aposaric

    aposaric Garden mechanic ;-)

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    I just did a complete front end swap on my '90 zx6d. I have put an USD front end from an zx7r. I have had new stem machined from high grade steel, and I bought new koyo bearings, so everything is the same as original on my new front end. The machining had cost me 40$ and new bearings another 30 $, and I think that it is the best and not to mention, the safest way to do this kind of a swap. I just wouldn't be comfortable having some 1 mm bushing standing between nice ride, and the visit to the hospital if it fails and my front wheel starts to wobble about :-) :freaky
    #11
  12. MILLENNIUM FALCON

    MILLENNIUM FALCON Been here awhile

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    Took it for a ride today.....handled great and felt much better than stock... Ill update you on the bushing wear.
    So Far I have a total of $53 in the fork swap. :)

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    #12
  13. DRjoe

    DRjoe Long timer

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    That is a cool looking motorcycle
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  14. 16VGTIDave

    16VGTIDave Reaver made me do it...

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    Lookin' good!


    Sent from my iPad2
    #14
  15. sailah

    sailah Lampin' it

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    I have some Yamaha fork guards off the KYB forks you can have for postage if you want them.
    #15
  16. MILLENNIUM FALCON

    MILLENNIUM FALCON Been here awhile

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    That is very kind of you. Just let me know how much and do you have a Paypal account?
    #16
  17. sailah

    sailah Lampin' it

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    I just went down and looked at them and one is cracked. Not sure its even worth the postage when you can buy new ones for about $25. Sorry for the false enthusiasm:norton
    #17