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Old 12-09-2011, 07:55 AM   #1
Havingfun OP
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Location: Plano, Texas
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Fender Bender on '91 GS

Out riding yesterday and found a corner that didn't want to be ridden. Consequently, I left the tarmac and found a fence. The good news is that I've got a bruise or two but that is the extent of my injuries, so no issues there. The bike was not so fortunate. It took a shot to the front end that twisted/bent the forks, I'm assuming (the handlebars don't point straight when the tire points straight), messed up the front fender and support. Those appear to be the major issues. The front wheel appears to be true.

So my questions are:
* if the handlebars and tire don't point the same direction, does that mean the forks are twisted?
* if twisted, can they be repaired or do they have to be replaced?
* are there other areas of damage I should look for if the forks are damaged?
* if I need parts, where can I find them?

Thanks for all the help on this.
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Old 12-09-2011, 08:19 AM   #2
One Less Harley
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Try loosening the clamps to get things back in line. This will tell you a lot. Sometimes that will be all it takes, just depends on how hard you hit. If you can't visually see if the forks are bent.You might want to pull off the top caps and remove the springs, wheel and fork tube brace. Slide each fork up and down and check for stiction.


If your forks are bent there are three or four options, straighten Forking By Frank, new sliders from Forking By Frank, Motobins or BMW. That's in order of preference and price.
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Old 12-09-2011, 10:08 AM   #3
baldwithglasses
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What about the stock fork lowers ("sliders")? How brittle are they? That is, can they catastrophically fail from impacts weeks or months after the incident occurred?
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Old 12-09-2011, 11:06 AM   #4
disston
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Quote:
Originally Posted by baldwithglasses View Post
What about the stock fork lowers ("sliders")? How brittle are they? That is, can they catastrophically fail from impacts weeks or months after the incident occurred?
Might not be an unheard of problem but I've never heard of it. I think you only need to be concerned at this point with damage you can see. Remove the damaged fender or anything else damaged that you don't need. The fender has no relation to the first phase of repair, that is having forks that go up and down. Try to twist or remount handle bars in proper relation to front wheel. They may only need to be put straight again. You'll want to carefully check important stress points like the axle/wheel bearing interface, the sliders ( see if you can see any scruff marks from impact). Are all the handle bar switches OK? If the bike runs can you ride it? After you straighten the handle bar does the bike go straight down the road? You might get back on the road sooner than you think but so far the amount of damage is not contained in your first report.

Charlie
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Old 12-09-2011, 11:38 AM   #5
Havingfun OP
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Good Advice...

OLH - I'll start with your suggestion. Good Idea and I'll keep Frank's info handy just in case.

BWG - I'll keep an eye on the lowers/sliders

disston - I was able to ride it home... about 60 miles but only at about 30 miles an hour, probably more of a function of me not knowing what all was wrong with the bike than the bike's ability. All the handlebar switches seem to be working. I think I used them all on the way home so they are good. I tried to twist the bars back straight but no success. Fender and brace are coming off this afternoon and I'll see about working on the top clamp. It is cold here today and the workspace isn't heated. Not too cold for riding, just too cold to sit in a garage

Thanks for the input.
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Old 12-09-2011, 12:02 PM   #6
CurlyMike
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I would be most concerned with the frame. Check the tabs that come from the frame up to the steering head. All else can be replaced with little effort. Where are you out? Might be able to come over and look at it and give you my 3 cents. PM me your number...
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Old 12-09-2011, 12:42 PM   #7
Toaster.Tan
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I did the same thing on my GS-PD (the tweak - not the fence). There are several quick checks for the forks to see if you can isolate the problem.

#1 - First and foremost: the brace bolted to the fork lowers is a thin, stamped steel piece of crap, which is why I now make a billet one of my own design. REMOVE IT, along with the fender.

#2 - Loosen ONLY the lower clamp on the tree - very loose. Whack the tubes with a rubber mallet a few firm blows to 'relax' them.

#3 - Place the POS lower fork brace on something smooth/flat and narrow so ONLY the holes touch where it mounts to see if it's tweaked (sits flat). If it doesn't you will need to un-tweak it before moving on. If it's flat - SET it on top of the mounting bosses on the lowers and see if the holes line up and sits flat without moving anything other than rotating the lowers. If the holes don't line up you MAY have bent tubes.

#4 - Tighten the lower tree clamp - then place the brace back on the boss and see if they now line up (or stay lined up). If they do you should be fine. If not refer to previous #3 SOL comment.

Rarely does the upper or lower tree clamps deform. More likely the tubes twist in the LOWER tree clamps when the lower steel brace bends and then are held in the twisted position. The lower fork brace is EASILY bent from minimal force - even turning the forks while in sand. It can be a test of patience to try to un-tweak it (technical term).

Last resort: disassemble the forks and roll the tubes to see of bent.

My 2


.
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Old 12-09-2011, 02:51 PM   #8
One Less Harley
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TT- I thought you only made the top brace, not the lower fork brace. Any picts of that?
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Old 12-09-2011, 03:01 PM   #9
disston
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Quote:
Originally Posted by One Less Harley View Post
TT- I thought you only made the top brace, not the lower fork brace. Any picts of that?
You're not the only one who caught that comment from TT. He's gotta know that with the one little slip now we will all want one.

Charlie
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Old 12-09-2011, 05:45 PM   #10
Airhead Wrangler
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Here is some historical reference. Please do not take it as a recommendation, but...
Somewhere in costa rica while riding down to south america a buddy of mine was paying a bit too much attention to the map on the top of his tank bag and not enough attention to the car in front of him which decided to stop. He didn't even notice the stopped car and did not brake. He plowed into the back of the car doing about 20 mph or so and launched himself onto the hood of the car. The front wheel of his heavily loaded GSPD was bent back far enough that it was stuck turned to the left and could not even be turned. He was ok and began asking around in the small town where he could find a hydraulic press. Sure enough there was a guy who had a pretty huge one. Off came the front end, the sliders came off the legs and the guy went to work bending them straight again. The guy obviously really knew what he was doing and was able to bend them pretty much perfectly straight again. The front end went back together and rode all the way down to argentina, back up to colombia, flew to florida, and back to BC again. Without further incident (well, not with the forks at least).
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Old 12-09-2011, 06:51 PM   #11
Toaster.Tan
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Quote:
Originally Posted by disston View Post
You're not the only one who caught that comment from TT. He's gotta know that with the one little slip now we will all want one.

Charlie
DANG! Noth'n gets past you guys!

I was just a tiny tad premature on that little disclosure - but I am meeting with my machinist and trailering my GS-PD to him. I've been pissed off ever since mine bent and decided to make one. Not only that... have not liked the aftermarket stuff - or lack of same - for that bike so am going to make several other things like....

Top clamp with some 'special' provisions
Risers and bar-backs of different height
Final drive torsion bar in billet (waaaay cool louvered I-beam)
MAYBE a bracket to invert the rear brake lever (problematic to do)

Hired a website designer today. Taking Toaster.Tan to the next level - - and keeping prices low. Did all y'all know I just lowered my prices on the top braces due to the new machinist I'm partnered with? He also has a special design machine with CAD/CAM that translates to the G-code for CNC machine. All in his.....GARAGE!

So that's whadup. When I get the design and validation parts made - I go public for production.



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Old 12-09-2011, 08:34 PM   #12
bereahorn
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Pm

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Old 12-10-2011, 01:27 PM   #13
Havingfun OP
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Update on Status

Well, I had time to look at the bike more closely today and the damage has grown a bit. The fender, fender/fork brace and the gas tank were removed. The brace was bent and will need to be replaced most likely. After loosening the bottom clamp I used the rubber mallet as suggested and then tried to straighten the handlebars. It appears the bars and forks are more closely aligned now but I'm not sure we have achieved complete success. There are a couple of other items that seem to have some damage; the handlebars and the roo bars. Without taking a close look the damage was not obvious. But the more I looked at it the more the image didn't fit my eye, if you know what I mean. It just didn't look right... because it wasn't. So the handlebars are slightly bent and the so are the roo bars, which pushes the dash slightly to one side. I don't know if it is a good idea to straighten (even though it is more of a tweak than bend) handlebars or to replace them once they have been damaged. Any input on this topic is appreciated. Also, are there good aftermarket handlebar options for these GSes?

One other item that was damaged was one of the steering stops on the bottom clamp. It wasn't sheared off but was damaged so that has to be addressed as well.

Thanks to everyone that has contributed to the triage effort and ideas. I'm not closing this thread off because the bike isn't fixed yet and there may be others with ideas and I am open to ideas so chime in if you want.

I'll provide status updates and the work progresses. I have a few days off work so I'll keep after the project.
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Havingfun screwed with this post 12-10-2011 at 01:32 PM Reason: added steering stop damage text...
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Old 12-10-2011, 04:33 PM   #14
One Less Harley
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Roo bars can be bent back, handle bars can handle a little tweak to get em back. I be one of your forks is bent just a little, at least going by your description.
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Old 12-10-2011, 05:42 PM   #15
disston
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I think it's perfectly OK to unbend handlebars. I don't know what A Roo bar is, have pity on me I'm an older rider. New lower fork brace replace sounds about right. I personally think they are really sacrificial parts, usually. The damage to the lower brace steering stop is a bad one. It would indicate the forks were at their full extent of turn and then some. Hopefully this is only a tweeked fork tube, most likely.

You are probably in need of some theory about what and how to deal with in this situation. Here is the fork straightening article by Randy Glass. It is a classic and even though work is being done on a much older Beemer, it's the theory that this should help fill in.

http://w6rec.com/duane/bmw/stiction.htm

Happy reading.

Charlie
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