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Thread: This is how the average guy can identify "bent forks"..............

  1. #1
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    This is how the average guy can identify "bent forks"..............

    It comes up allot, I've posted this in threads abut never made a fresh topic about it.

    Some may or may not agree, but if done as posted you will not harm anything.......

    Not EVERYONE has V-blocks and a dial indicator setup.

    Jack it up and get the front tire an inch of of the ground.

    Remove the upper fork boot clamp or plastic strap and lower it as low or SQUASHED as you can get it.

    Loosen all 8 pinch bolts (or whatever) and make sure they are about 1/8th inch loose or away from where they would lock down on the triple clamp. I usually take the top bolt out completely and angle my screwdriver down.

    Get 2 flat head screwdrivers that will fit in the "gap".

    GENTLY tap them in to spread the open aluminum just a hair; Any more isn't needed. If you spread them too much, the leg starts to drop out and the aluminum is weekend; You run the risk of snapping the ear off. Just a gentle tap until it turns is all you need.

    Try one side at a time and barely tap/tighten them in until the upper tube can be rotated by hand.

    Rotate the upper fork tube by hand, may require a bit more tapping of the screwdrivers. Do not hit the chrome portion of the tube while doing this, just angle the screwdriver. I use 2 identical medium sized screwdrivers.

    As it turns, with the wheel slightly off the ground, you will see the wheel/axle change angles or the lower fork leg moving back and forth or in a circle.

    If they remain straight, your good

    If they do as suggested above, then the upper chrome tube is bent. It isn't the end of the world, MANY trike forks are bent! The 200X fork seems to bend very easy after a crash/roll etc etc.

    A good machinist/mechanic can fix them with 3 V-blocks and a 10-20 ton press or even an arbor press. If they are just a bit bent, there won't be an issue bending them back. If they are kinked or that wheel moves like crazy! when you rotate it, it's best to get another set of forks or good upper tubes. I've been amazed at how much it changes the wheels axle location when there bent pretty good!

    Another method of (careful gap spreading) is to use a fully threaded bolt and thread it in from behind. Place a penny in the "gap" and thread the bolt in until it touches the penny, then tighten it a hair more or until the gap spreads a bit (DON'T OVER DO IT!!) Then you can rotate the tube as suggested above. This is the same method I use to "spread" rear axle carrier pinch bolts so I can tap the axle carrier out without damaging it.........

    The problem is that some or many upper fork tubes are pitted with rust. If the rust is within the triple clamps, then it's merely a cosmetic issue. If they are pitted under the fork boot then they eat up seals pretty quick.

    How to unbend them is a whole other Topic. I can usually get them very close in my shop or if you are equipped (or have a bud with the goodies - 3 V-blocks and a good indicator) you can do it yourself.

    Of course the best way is to disassemble them and put the upper tube in 2 V-blocks using a dial indicator. But not everyone can do that, yet they still want to know how to identify "bent forks"!!

    Follow the directions above and I hope it helps some guys figure out whats going on!

    DC
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  2. #2
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    Dam DC you are a wealth of knowledge

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    I just "bent back" a set of bent froks today, the ones that came off my 84' 250R project. They are actually 85' front forks. I found it rather strange that one fork was bent bad, and the other was straight!? Anyway, I work in a machining shop, and they have all the goodies! I dis-assembled the fork, and put the chrome tube in some v blocks, and put it under the hydraulic press. I used the manual press mode (hand pump) and found the high spot on the bend. Next I bent the fork back down, and you actually have to go well beyond the bend, and when the perssure comes off, the fork springs back up. Did it by eye, then rolled it on a flat surface, and it rolled smoothe and straight! Also put it in the lathe for shits and giggles, and it spun decently straight. Worked perfectly. This is the second time I have done this now, its really easy to do, and only takes about 10-15 minutes. Now im waiting for the fork seals to come in, so I can get em' back together. Completly disassembling them is the key, and makes dealing with them a lot easier. Good topic Dirtcrasher!
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  4. #4
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    Thanks guys, just trying to share



    This one shows how far you sometimes go PAST straight:



    Yes, I use to use wooden V-blocks
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  5. #5
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    Never heard of that technique before. Cool tip for checking while the forks are installed. Thanks for posting it.

    Here's an easy one for forks that aren't mounted on a trike (real simple for simple minded people like myself ).

    Lay the fork on the ground along one of the lines in your driveway. Hold the lower section firmly to the ground with your knee. Rotate the chrome tube by hand while watching the very top of the fork. With it lined up against a straight edge (the line in the driveway) you'll easily be able to see if it's bent or not as it rotates.

  6. #6
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    Thanks Dirtcrasher. What does the block look like that is pressing against the tube? It looks like its machined out, to create a half circle.
    84 200x

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    ^ I cut a half circle out of a wooden block before I got 2 more V-blocks....

    The block on the ram is an actual V-Block, I didn't want to crush the tubes.
    Last edited by Dirtcrasher; 05-09-2010 at 07:42 PM.
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  8. #8
    250rAL is offline Just Too Addicted Arm chair racerJust too addicted
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    I know mine has one slightly bent fork. When I pull the machine backwards, the front wheel will turn to the side. Is that because of the bent fork or do they do that even with straight forks?
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  9. #9
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    I did a modified version of this check while tearing down one of the Ugly Twins (84 200x). Once I got the front wheel off, I loosened the triples and spun the upper tube in the triples. One fork is visibly bent, on isn't. Visibly bent = slider moves while I spin the upper. No kinks in the tube, just bent.

    No worries - I need to take it apart anyway for cleaning and oil change. The worst part is finding a machine shop I trust...

  10. #10
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    I find almost every 250SX and 200X fork to be bent.....

    Right where it meets the lower triple clamp!

    The only issue is it will eat away at the coating on the 2 bushings and someday those will be discontinued if not already.

    You can always take it apart and send me just the bent tube, saves allot on the shipping.
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  11. #11
    racerxxx's Avatar
    racerxxx is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    DC,

    Nice write up, I bent my 200x forks back with the V block method at my father in laws machine shop.

    My personal favorite picture is of your micrometer "C" Clamp!!!!!!!
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  12. #12
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    Yo DC, any tips with solid ole hardtail forks?

    Same idea? I might be picking up a 110 and it looks like someone hit a tree doing 55!
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  13. #13
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    For those I'd use a straightedge.....

    Some of the guys with 110's could tell you the rake give or take and I've checked that with a magnetic base angle finder

    RacerXXX - Thats the nearest clamp I could find Thats an ENCO cheapo, the good one never gets a spanking.....
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  14. #14
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    Quote Originally Posted by Kintore View Post
    Yo DC, any tips with solid ole hardtail forks?

    Same idea? I might be picking up a 110 and it looks like someone hit a tree doing 55!
    DC your def the man !

    110 forks are a pain to straighten but a 4' straight edge and a few trial and eras on the press and their fixed .
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  15. #15
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    thanks guys!
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