Bent triple tree

Discussion in 'Tech Area' started by Kobwo, Jun 19, 2018.

  1. Kobwo

    Kobwo New Member

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    hello all, looking for a bit of advice. As with most of these bikes they’ve been laid down and over the years those front forks take a beating. My K0 tracks straight BUT the triple tree upper and lower tube forks are bent. The front fender points to the left a little bit. I’m going to replace the lower forks with new but unsure what to do with the upper fork tubes attached to the triple tree. Maybe take it into a motorcycle frame shop? I also am going to replace the handle bars with CHP Repros. I’d like everything to track straight and be lined up straight but those fixed tubes need to be made straight again.

    Thanks for any input in advance
     
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  3. racerx

    racerx Administrator
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    Got any pix?
     
  4. Sidewinder

    Sidewinder Well-Known Member

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    Boy, it'd take quite a wreck to bend those tubes on the triple tree... but I suppose it could be done. If the bend is slight, how about inserting a snug-fitting metal rod up almost as far as the bend, heating the tube, and using the rod as a lever to bend the tube back into place? You'll ruin the paint, but that's what I figure any cycle shop would do... or try as a fix first. Might even be able to bend the tube back into place without heat, the help of a good bench vise and/or a couple of burly friends is recommended, LOL. The way you described the bend(s), and the way the fender sits, it doesn't sound like those triple tree tubes bent too far... the fender itself may be out of whack from some past wreck. RacerX has the right idea (as usual, LOL)---before ya do anything, get some pics of the triple tree tubes from the front and sides, maybe some other angles like top down, that'll show the damage. WTF, include the lower fork tubes in the pics, even though you're better off just swapping them out... the damaged ones might give clues about what happened to the triple tree. :confused:
     
  5. lukelaw1

    lukelaw1 Active Member

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    The front fender usually has some play in it when bolting up. Lossen the three fender bolts and see if you can move the fender and cheat it straight. Also may just want to take the fender off and see how it sits on a good flat surface. The fender front lip may have been used as a grab bar a one point in its life, usually twisted and all four corners won't touch the table. It will rock back and forth if twisted.
     
  6. cjpayne

    cjpayne Well-Known Member

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    I bet kirrbby could straighten it with two pieces of wood and a vice.
     
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  7. racerx

    racerx Administrator
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    You forgot about the BMF hammer, cj.:cool:
     
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  8. dirtbkr188

    dirtbkr188 Active Member

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    I've had this happen to me on a few occasions with mid '80's Z50R models that I had. I can't explain why, but the bars/top triple would be slightly offset to one side or the other, not perfectly in line with the front wheel and frame. Everything looked fine, no cracks or broken welds (that I could see) where the fork tubes are attached to the lower triple. It just seemed to have a slight "flex" to it, and I simply realigned everything by smacking a tree with the front wheel, much like I used to do as a kid with my bicycle. Granted it didn't make for a permanent fix to the issue, but everything lined up straight, at least until the next time I crashed.
    I honestly never let it bother me, the bikes were backyard track-n-trail riders for overgrown 8-year olds, and were only capable of 0 to 34.57MPH sometime before the sun goes down.
    If anyone has experienced this and can explain why this happens, and how to fix it, I'd be curious to know.
     
  9. cjpayne

    cjpayne Well-Known Member

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    Lol. I wonder how big the biggest hammer he has actually is. Maybe he'll post a pic.
     
  10. Kobwo

    Kobwo New Member

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    Sorry for the late reply. Been out of town for a while. I took a few pics. This is after replacing the crooked handlebars with CHP replacements. As for the triple tree, you can see a little bit of wrinkling in the tube under the lower brace. Right up next to it. I didn’t get a pic of this but I can see some light wrinkles and feel it with my hand. Here are the pics both with the tire straight on and with the handle bars and light pointed straight.
     

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  11. racerx

    racerx Administrator
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    Looks fine...on this tiny screen.:whistle:
     
  12. Kobwo

    Kobwo New Member

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    Unsure how to take a better pic to highlight BUT when I track with the handle bars/ headlight straight to the centerline of the bike, it takes a right hand turn.
     
  13. wanrep

    wanrep Member

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    Need a pic or 2 from the side.
     
  14. Kobwo

    Kobwo New Member

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    Ok
     
  15. kirrbby

    kirrbby Well-Known Member

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    I've seen a couple where the triple tree itself was bent below the plate, toward the rear of the bike. Like if you were to ride the bike into a open manhole and hit hard. ;--/

    More common is when the tubes are just twisted/tweaked a bit.

    You can usually see either by eye.
    Sight across the two front tubes from the side, looking only at the front edges, to see if they are parallel. If they are out, you should see one sticking farther forward than the other at the top, and farther rearward at the bottom. This can usually be corrected like CJ said, with two pieces of pipe stuck up into the tubes to use as leverage to simply tweak them back straight. You really need to remove the triple tree completely to do this job, but you might be able to do it with only the front wheel, AND the top plate/bar clamp removed.

    If one of the tubes are actually bent, as in NOT a straight pipe anymore, I'd scrap the triple tree and buy a good used part.
    I can usually tell if one is bent by looking straight down each tube, from the front, then from the side. If one looks roundish, or kinked at the plate, I'd call it scrap. Even if you could get it back close to straight, it will not be perfectly round, on the inside, anymore. That will cause the inner guts to hang up, wear badly, etc.
     
  16. racerx

    racerx Administrator
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    I check fork legs by rolling them on a known, flat, surface. Slight bends can be corrected but, for most, that repair carries a difficulty rating of 12 on a 1-10 scale. There are shops that can (or should be able to) do this, probably just easier to source a straight fork leg.
     
  17. kirrbby

    kirrbby Well-Known Member

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    As a brand new 135# 20 year old apprentice carpenter, my friend told me to get a 28oz Vaughn wood handled framing hammer with a waffle (meat cleaver) milled face. Which I did. My first framing hammer. Looking back I wonder if it was only for his own amusement.

    After using that beast for a while, I realized that the hammer does NOT make the man. These days, a 16" Craftsman 20oz smooth face rip hammer with a fiberglass handle is my go to. Also a 14" tru-temper 20oz fiberglass rip is a favorite as it's adequate for most and much easier to carry on the tool belt, or in hand.

    Here at work I carry a 18" Dead-On wood, hatchet handled, TITANIUM framer, that is only 14oz. Huge titanium head, but light. Long handle and light head, gives you a long fast stroke...it's a great hammer too, but pricey.
    But then, it IS my #1 tool. What's a couple hundred bucks when you're buying a new friend.

    IMG_20180711_111921521.jpg IMG_20180711_111951062.jpg
     
    #16 kirrbby, Jul 11, 2018
    Last edited: Jul 11, 2018
  18. Kobwo

    Kobwo New Member

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    Thanks for the insight. I looked on eBay for a new old triple tree and it’s hard to discern if those old ones are straight or not. I’d hate to order one to have the same problem.
     
  19. racerx

    racerx Administrator
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    I went back to view your pix on my desktop monitor and can now see the twist, somewhat. On my phone's tiny screen, it was hard to tell that this is a K0 front end. As for seeing the "wrinkling in the tube"...fuggeddaboudit! That impacts my suggestions. A bent upper fork...which includes the integral lower tree...is pretty easy to see with a K0. And, straightening a tweaked inner (lower) fork leg is a lot easier than with any of the later model hydraulic forks. The pogo stick internals are nowhere near what I'd consider precision mechanicals.

    That said, I've seen a lot of tweaked K0 upper fork units. They're rarely bent; in a crash, it's the lowers that sacrifice themselves, probably 95% of the time. However, that thin, steel, lower tree is flexible (until everything is assembled & torqued). The upside of this being the fact that the upper legs can be tweaked back into alignment (i.e. parallel from side-to-side) by hand. And as kirrbby pointed out, that may be all that is needed to get the front wheel on the same midline as the rear.

    OTOH, if your upper/outer fork tubes are bent, it's far easier to just source another upper fork that is still straight. There's no way to straighten the uppers without involving a repaint, so why go through all of the extra effort of wrestling with damaged parts that are easily & inexpensively replaced? It'd be merely a question of whether you prefer paint work with, or without, metal wrangling.

    "if it won't go...hammer it"?:ROFLMAO:
     
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  20. kirrbby

    kirrbby Well-Known Member

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    Ya, it is tough to tell unless a experienced eye, eBay seller has looked and confirmed that they're straight.
    You only need a part that has good ears and acceptable paint, plus...the tubes have to be straight. If they're tweaked a bit, it's no problem. But you should confirm that yours is bad before you risk buying a used part.
    Unless one of the tubes...of the lower triple tree... is bent, you should be ok. Just buy new chrome inner legs, then straighten the triple tree if necessary.
     
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  21. Kobwo

    Kobwo New Member

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    Thanks for all the replies. I figure lol try the straightening method first, it doesn’t need much massaging. If it doesn’t work out I’ll hunt for replacement. It’ll also give me a chance to rebuild the forks as well.
     

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