Something Bent? - Wrist Twisters
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  • 1 Post By Trailing_Throttle
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  • 1 Post By nathanktm
 
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post #1 of 5 Old 03-26-2019, 05:54 PM Thread Starter
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Something Bent?

I went down with a lowside on track last july (35-45 mph). A few things touched down but it was a pretty soft down, and the damage was pretty minor considering it was a track spill. The only thing I had to replace was the front fender. The forks themselves did not touch the ground.

Link to post-crash damage photo - http://puu.sh/D5PFP/4e3f062e30.jpg

The biggest problem was that it tweaked my steering. I managed to get it -close- but never straight. I've been riding around with my bars like that since then, and I finally changed the fork oil and figured redoing the whole front end essentially would wind up with everything straight, but it's just as crooked as it was before. I've tried loosening every single thing south of the two top pinch bolts on the top yoke, and the giant triple tree nut right under the bars as well, wiggling everything around and compressing the forks, and it settles in the same spot every time.


I'm not sure what I should do, or what/how I should check to find the cause of this problem. My immediate guess would be that the right fork is bent inwards, but I'm not sure how I could check that since it's so slight, or why it would be bent when it's never hit anything.

The image below is how the bars currently sit.


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post #2 of 5 Old 03-27-2019, 05:52 AM
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You need to get the bike up on a pit stand, sitting vertically and find out how the rear wheel aligns with front. It's possible that the rear wheel was offset somehow in the crash....er..."impact setback" and it not being aligned with the bike centerline could result in the steering offset you see. However, to be fair, what you show is a lot of offset and it may be too much to be explained by rear wheel off-tracking. It may be that something is bent someplace and you may need professional help to figure it out. http://gmdatl.com/services.html for example.
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post #3 of 5 Old 03-27-2019, 03:15 PM
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Could be a torsional twist of the triple clamp. Get the front end up in the air and remove the forks. If they BOTH slide in and out of the clamps easily then the clamp is likely NOT bent. Outside of that little test we pull the forks apart and see if the inner stanchions are true or not.
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post #4 of 5 Old 03-29-2019, 06:17 PM Thread Starter
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So I may have fixed it. I can't be 100% sure yet as I haven't ridden the highway, but a lap around the block and it seems straight now. I loosened just the upper yoke, and gave the bars a couple tweaks and bounces, tightened those and then did the bottom again/front wheel installation procedure and it seems to be straight now. I also spun each of the fork legs 180 degrees inside the yokes and they didn't bind up at all and it made no difference to the alignment.

Sent from my SM-G950U using Tapatalk
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post #5 of 5 Old 03-30-2019, 06:51 PM
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Quote:
Originally Posted by nathanktm View Post
So I may have fixed it. I can't be 100% sure yet as I haven't ridden the highway, but a lap around the block and it seems straight now. I loosened just the upper yoke, and gave the bars a couple tweaks and bounces, tightened those and then did the bottom again/front wheel installation procedure and it seems to be straight now. I also spun each of the fork legs 180 degrees inside the yokes and they didn't bind up at all and it made no difference to the alignment.

Sent from my SM-G950U using Tapatalk
If it nicely tracks straight with the bars centred, then it sounds as though you got away with it.

In addition to what the others have already covered, also keep in mind that IN GENERAL re conventional forks with lower legs (non USD):
1
Fork tubes bend before triples do.
2
Fork tubes first bend somewhere below the triples.
(where they bend can be a real mystery, but it will be above the upper bushing's position on the fork tube at the instant the energy input occurred)
3
Fork tubes bent between the triples is consistent with major to severe incidents.
4
Fork assemblies with tubes lubricated for easier fitting into the triples, are more likely to twist, than those fitted dry into triples that have good bores "showing" lots of contact area, and are properly torqued.

Forks are best V blocked and dialled to check straightness.
Proper checking dictates numerous tests with the V blocks in different positions.
First is end / end.
Second is where the two triples rest.
Third depends on what the first two reveal and/or suggest.

Even rolling a bare fork tube on a good flat kitchen counter will reveal significant bends.
(but not small ones that will very much be problematic re bushings and seal wear)

Fork tube straightening is an art type skill.
Some are real maestros at it.
Others are hackers.
I think it's in the same league as really good built up crank shaft builders.

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