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Author Topic: big bump at speed - what did I break?  (Read 1331 times)

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Offline c(b)hris

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big bump at speed - what did I break?
« on: June 28, 2011, 09:37:56 PM »
75 CB550K

I was riding on the interstate at about 75mph and hit a huge bump.  It felt like the bike came off the ground.  Now my steering doesn't feel so stable.  I rebuilt the forks and replaced the fork seals about 1800 miles ago.  What should I check besides alignment?  Could I have blown a fork seal?  I don't see fork oil leaking anywhere, but the front feels 'squishier' than before.  When I coast down to the end of my driveway, when I hit the brakes I can tell the forks are compressing, where as before it wouldn't have been noticeable.  Any advice is appreciated, thanks.
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Offline Retro Rocket

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Re: big bump at speed - what did I break?
« Reply #1 on: June 29, 2011, 12:03:28 AM »
You may be just imagining the compression thing, all suspensions compress under brakes and even if you didn't notice it it definitely happens. Under the weight of a 750 you will experience almost full suspension travel even at slow speed when applying the front brake to a dead stop. Your suspension would have bottomed out when hitting the bump, maybe even jarring your wrists, this has happened to me before as well, as long as you have checked everything and its all still straight and  all bolts are tight, you should be ok. Just check the clamps for any fractures.
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Offline MoMo

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Re: big bump at speed - what did I break?
« Reply #2 on: June 29, 2011, 05:52:24 AM »
Check the rim too, it could have bent but I doubt it...Larry
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Offline Pinhead

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Re: big bump at speed - what did I break?
« Reply #3 on: June 29, 2011, 10:12:03 PM »
Make sure you didn't crack the triple trees.
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Online seanbarney41

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Re: big bump at speed - what did I break?
« Reply #4 on: June 30, 2011, 03:15:26 AM »
Do you have the stock ball bearings or tapered roller bearings in the steering head?  I can see a big bump settling 'em in significantly or possibly damaging 'em(although that wouldn't explain the forks compressing easier)  Do the steering adjustement in the manual where you jack the front end off the ground and adjust the steering stem top nut with a spanner.  If when you tighten the nut, the steering gets seriously notchy or bindy(is that a word?), I bet you damaged your bearings or races...
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Offline Hush

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Re: big bump at speed - what did I break?
« Reply #5 on: June 30, 2011, 03:36:58 AM »
If you have to old roller bearings still in there you can split them like peas if the steering nut is not torqued correctly.
But I'd be looking for any stress fractures esp at the bottom of the steering stem, these have been shown to be fractured on quite a few 750's on here when forum members have bought bikes to restore.
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Offline fmctm1sw

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Re: big bump at speed - what did I break?
« Reply #6 on: June 30, 2011, 04:16:28 PM »
Quote from: Pinhead on June 29, 2011, 10:12:03 PM
Make sure you didn't crack the triple trees.

+1.  Top clamp.  I broke mine hitting a bump ...
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Offline c(b)hris

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Re: big bump at speed - what did I break?
« Reply #7 on: June 30, 2011, 04:27:06 PM »
top clamp looks okay.
tapered roller bearings already installed.
it felt trustier today, but I wonder if Im just getting more used to it.
I also never noticed the bike going down as much in the back when I sit on it as I do now.  Maybe I should just lay off the fast food.
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Offline Jim F

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Re: big bump at speed - what did I break?
« Reply #8 on: June 30, 2011, 04:54:06 PM »
Just a thought but maybe you collapsed a spring in your forks?
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Offline donpark1086

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Re: big bump at speed - what did I break?
« Reply #9 on: June 30, 2011, 06:01:43 PM »
Don't ride it until the problem is diagnosed and fully corrected.  Be safe.
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Offline Hush

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Re: big bump at speed - what did I break?
« Reply #10 on: July 02, 2011, 11:34:50 AM »
I would ride it carefully, maybe it is a case of getting used to it after mods.
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I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline crazypj

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Re: big bump at speed - what did I break?
« Reply #11 on: July 02, 2011, 12:04:56 PM »
First, did anyone read initial post?
ITS A 550  ::)
 I beat the hell out of mine, including taking it around a motocross course on more than one occasion   ;)
(I subscribe to the 3'R's', ride it, reck it (sic), repair it  ;D )
 Anyone who broke a top yoke hitting a bump either didn't have things tightened or hit something line a 6" kerb bending forks backwards.
 It's more likely things were not lined up right, they are now so forks are actually operating as they should.
« Last Edit: July 02, 2011, 12:07:08 PM by crazypj »
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Offline Hush

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Re: big bump at speed - what did I break?
« Reply #12 on: July 03, 2011, 09:43:42 AM »
550/750 big difference not, forks are forks, steering stems are steering stems. ;D
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I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline crazypj

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Re: big bump at speed - what did I break?
« Reply #13 on: July 03, 2011, 04:51:12 PM »
About a 100lbs, with momentum, BIG difference
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