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Old 11-22-2010, 11:46 AM   #1
mfp4073 OP
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occasional wobble in my front end, 74 /6

Occasionally, not all the time I will get a wobble in my front end/handle bars. At first I thought it was a symptom of concrete grooves, or wind buffeting of my throttle arm.

I dont have a cresent wrench or metric wrench big enough for the nut on top of the tree (that the steering damper adjuster goes through). I have used a big pair of adjustable pliers just to test it for looseness gently and didnt find anything. I have also tried "rocking" the handlebars to find looseness or play in the bearings of the fork pivot (dont know the proper name) and not come up with anything. Tried for movement in the front bearings too (rocking handlebars, or movement in the front wheel that should not be there).

It does not do it all the time. And sometimes I can make it do it by kinda, jacking one side of the bars with my hand. Usually just firming up my grip on the bars makes it go away.

Any ideas?
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Old 11-22-2010, 12:15 PM   #2
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I think the assembly at the top-o-fork is commonly called 'steering head' around here.

If you can't find any loosness in bearings, it sounds like a precursor to the vile & dreaded "tank slapper". Does your steering damper work and is it easily adjustable?

I'm sure others will have more experienced words, til then you might hint at when it is felt.
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Old 11-22-2010, 12:53 PM   #3
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Fork issues:
With the bike on the c-stand, move the fork back and forth to feel for and notching or binding. If centered and gently pushed to either side (steering damper off) the fork should fall gently, but deliberately to either side. Grasp the fork bottoms and rock fore and aft, feeling for ANY movement. With you on the bike and off Cstand dive the forks with the front brake applied. Any clicking? do they return consistently?
Wheel issues:
Front wheel still off the ground, push on the sidewall of the tire with your hands at the top near the fork leg, using the leg for leverage. If you feel ANY notchiness, your wheel bearings are suspect. Spin the wheel slowly feeling for roughness while ignoring the disc drag noises.
Front tire:
Aging, cupping, inflated properly? Any of these can transmit weird pulses at odd times.
Other:
Check your swing arm bearings for play as well as rear wheel. Low on the likely suspect list, but everything is attached and works together.
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Old 11-22-2010, 01:52 PM   #4
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Quote:
Originally Posted by mykill
Fork issues:
With the bike on the c-stand, move the fork back and forth to feel for and notching or binding. If centered and gently pushed to either side (steering damper off) the fork should fall gently, but deliberately to either side. Grasp the fork bottoms and rock fore and aft, feeling for ANY movement. With you on the bike and off Cstand dive the forks with the front brake applied. Any clicking? do they return consistently?
Wheel issues:
Front wheel still off the ground, push on the sidewall of the tire with your hands at the top near the fork leg, using the leg for leverage. If you feel ANY notchiness, your wheel bearings are suspect. Spin the wheel slowly feeling for roughness while ignoring the disc drag noises.
Front tire:
Aging, cupping, inflated properly? Any of these can transmit weird pulses at odd times.
Other:
Check your swing arm bearings for play as well as rear wheel. Low on the likely suspect list, but everything is attached and works together.
Good info, tire pressure and bad shocks can be a factor also.
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Old 11-22-2010, 03:47 PM   #5
Rob Farmer
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When were the wheel bearing pre loads last checked? I had a similar issue with my 100/7, checked the bearing pre load and it was way too loose. new bearings and a reshim and alls well. Mine did it if I took the weight of my arms in a gentle bend, just a little rocking of the bars that went away if you gripped them though I did feel it would have developed into a big occasion if I'd have let it carry on.

Rob Farmer screwed with this post 11-22-2010 at 03:53 PM
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Old 11-22-2010, 05:13 PM   #6
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When was the last time your wheel was balanced? You never know, lets hope it's something simple and cheap!
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Old 11-22-2010, 06:25 PM   #7
Bill Harris
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It may be something as simple as tires or shocks, but thius is a good opportunity to chack the head bearings, the wheel bearings and the swingarm bearings, as well as the spoke tension. That wobble can end up killing you and this is a good time to do that maintenance.
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Old 11-22-2010, 08:07 PM   #8
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All good suggestions. Also, check the bolts that secure the subframe to the frame as well. It's all a system from the rear tire patch through the wheel bearings, the swingarm, frame, steering head, forks, etc. Many links, none stronger than the weakest.
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Old 11-22-2010, 08:45 PM   #9
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Thanks, all good stuff to check and look into.

Steering damper turns two the three positions, but I dont know that I can tell much difference in them.

Bike is new to me, about 4-5 months old now. I dont have a detailed service history of it prior to getting into my hands, but the PO really seemed to have done a great job of doing everything and doing it right.

My "non-motorcycle automotive mind" says that its in the wheel bearing or the steering head bearings as just a "feeling" and probably a preload issue. Will look at the stuff again with the ways recommended.
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Quote:
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loner, lonegunman, get it. Thatís the whole point. I like the lifestyle, the image. Look a the way I dress.
Quote:
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Cavemen must've designed them shortly after inventing the wheel.
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Old 11-23-2010, 07:00 AM   #10
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Ironically, steering head bearings that are too tight can feel twitchy at speed, too.
Another thing I noticed is a top box that sits back and high with weight in it can make the front end wander. At speed, the front wheel is just barley touching the road.
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Old 12-02-2010, 03:33 PM   #11
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Went through today with another set of hands. Wiggled and shook and checked for looseness, but didnt come up with anything. In the last several days I have been able to "make it" do it a little more often if I am in 2nd or 3rd, rpms high and then cut the throttle with a loose grip on the bars. It seems to recover if I either give it some throttle or grip on bars and use my arms as the dampener. I cannot make it do it with the front brake (to dive the suspension) but then there is no way to use the front brake without a decent grip on the bars. Rear brake just wants to lock up, so not getting the same stopping with it.
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Quote:
Originally Posted by Martin Blank
loner, lonegunman, get it. Thatís the whole point. I like the lifestyle, the image. Look a the way I dress.
Quote:
Originally Posted by bgoodsoil View Post
Cavemen must've designed them shortly after inventing the wheel.
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Old 12-02-2010, 04:54 PM   #12
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Just remember that all bikes can head shake at times. Especially coasting down through the 45 to 35mph speed zone. I have read some claim that they can make a bike completely wobbe/head shake proof. BULL @*#$!
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Old 12-02-2010, 05:56 PM   #13
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I was experiencing some wobble on my 76 r90/6 at around 40mph, and it was especially prone to happen on deceleration. I could always stabilize it with some pressure on the bars.

I replaced the front tire that was on the bike when I bought it about about 5 months ago (metzler, still looked like it had *some* life), and the shake is gone. Obviously, YMMV. Good luck!
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Old 12-02-2010, 07:31 PM   #14
mfp4073 OP
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tire is a metzler lasertec I think. It was new when I got the bike, but has about 4500 miles on it now. something else to add to the list.
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1974 BMW R90/6 Bettie #1, 04 Triumph Bonneville
Quote:
Originally Posted by Martin Blank
loner, lonegunman, get it. Thatís the whole point. I like the lifestyle, the image. Look a the way I dress.
Quote:
Originally Posted by bgoodsoil View Post
Cavemen must've designed them shortly after inventing the wheel.
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Old 12-02-2010, 07:57 PM   #15
mykill
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cupping

Lasertecs seem to be proone to cupping which can do wierd things to steering and general front end feel. 4500 miles and age could be factors. If they are crusty or you can notice highs and lows over the circumference suspect the tire.
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