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Old 11-04-2013, 12:52 AM   #1
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Headhshake...urgh...

I have an '06 1200GS (40, 000 miles) which *seems* to be exhibiting some headshake. I'm not quite sure what's causing it, though. The headshake is present when accelerating, particularly uphill, and when passing cars and/or changing lanes quickly, all while under hard acceleration. The headshake isn't violent (once it was, just accelerating hard up to about 90mph) but it's very disturbing.


The Ohlins front and rear were just rebuilt last winter, but the issue was present prior to that I've had a somewhat "down" season without as much riding as normal).


Yesterday I visited a very well known and knowledgeable Japanese bike tuner here. He has worked on BMWs a lot, including GS's. His immediate remark was how light my steering head bearing felt. Though no play or notchiness is felt, it just feels sooooo light. His suggestion was to enjoy the rest of the season (I can mitigate the shake with a stabilizer and the preload in the rear cranked a bit) and to bring it to him once the nice weather is finished.

I suppose that the super light feel in the bearing is a bad thing...how do I "test" it or get an idea of it's out of spec, or if it just needs to be tightened, or what? Can you guys give me some advise? Thanks!
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Old 11-04-2013, 01:03 AM   #2
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don't know what your particular problem is but I had what I thought was a front end shake... that turned out to be the rear tire. I was surprised to find out the vibration that seemed to be coming from the front was in fact being caused in the rear, and I am not saying this is your problem either but something that brings my entire to shakes/vibrations/noises and ensuing troubleshooting process.
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Old 11-04-2013, 01:10 AM   #3
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I have felt it on two rear tires so far... (first was a TKC so it didn't last very long)
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Old 11-04-2013, 01:33 AM   #4
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my first idea would be tires...i have the same issue when hard accelerating with the K60 Scout ... when the front wheel gets lighter its prone to shaking... not sure about the TKC
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Old 11-04-2013, 01:49 AM   #5
Bill the Bong
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Remove some rear preload or add front shock preload.
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Old 11-04-2013, 06:20 AM   #6
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Quote:
Originally Posted by Bill the Bong View Post
Remove some rear preload or add front shock preload.
That often helps, but since he had it with old and new shocks, it probably isn't the issue.

What aftermarket windscreen do you have and how tall are you?

On my 05 I get some headshake when I switch to my winter screen, a Givi screen.



Stock screen I get nothing. I am only 5'8" tall, so YMMV.

Jim
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Old 11-04-2013, 06:39 AM   #7
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I'm also 5'8". I have both a short summer screen and a normal height original BMW. It happens with both.

I can try to add preload on the front (and reduce in the rear) but dang adjusting preload on the front is hard to do...it's very difficult to reach up there, any tricks?


Does anyone think this "head bearing has too little resistance" argument really holds water? (theoretically it does, but...hmm) Can I give it a little turn or two?
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Old 11-04-2013, 06:47 AM   #8
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I'm also 5'8". I have both a short summer screen and a normal height original BMW. It happens with both.

I can try to add preload on the front (and reduce in the rear) but dang adjusting preload on the front is hard to do...it's very difficult to reach up there, any tricks?


Does anyone think this "head bearing has too little resistance" argument really holds water? (theoretically it does, but...hmm) Can I give it a little turn or two?
If there is no slop in the head bearing it is not an issue. Make sure your telelever bearing has no slop. Likely it is in your shock set-up if screens do not matter. I misread your post, so you have the same shocks, just rebuilt? Probably the same settings too.

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Old 11-04-2013, 07:13 AM   #9
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How do you (I) check the telelever bearings?

The shocks are Ohlins...any tricks on getting to the preload adjustment easier than finding a strong 3 year old (tiny hands)?
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Old 11-04-2013, 07:22 AM   #10
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Checking the telelever is as simple has holding the brake and rocking the bike forward and back. You can visually see the ball bearing move if it is worn.

As for adjusting the front shock, I usually just take it loose from the top, but it can be done without doing that.

Jim
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Old 11-04-2013, 07:46 AM   #11
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I wonder if I checked the head bearings incorrectly... Bike on centerstand, pull and push at the end of the forks, no movement fore and aft...correct method?
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Old 11-04-2013, 01:39 PM   #12
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I wonder if I checked the head bearings incorrectly... Bike on centerstand, pull and push at the end of the forks, no movement fore and aft...correct method?
I don't think you could be sure on the centerstand. I do it standing uptight off the stands, front brake held. Usually easier to see if someone else is rocking the bike while you look at the ball joint. If it is loose it is pretty obvious.

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Old 11-04-2013, 06:29 PM   #13
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I too would start with the easy stuff. Tires especially. I've found that typically a front out of balance shakes while decel but not uncommon under accel as well. Rear tire could be bad or out of balance too like other have suggested. I just had my first belt separation on a michelin rear. A first in 30 years of riding. It felt like the rear was 'wagging'. No other way to explain it but it did transfer some vibes to the bars too. I'd maybe pull the front and try a balance first and check for bad cupping. How many miles on front tire? Yes, it could be bearings, but highly unlikely for that mileage for a BMW IMO.
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Old 11-05-2013, 12:05 AM   #14
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Well, this is the second front it's done it on. This one has about 400 miles. It had a pretty big slapper with less than 100 miles on it.

I'm tempted to try to balance it again at home and see what happens...
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Old 11-05-2013, 06:42 AM   #15
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Well, this is the second front it's done it on. This one has about 400 miles. It had a pretty big slapper with less than 100 miles on it.

I'm tempted to try to balance it again at home and see what happens...
Hmmm, I assume the front rim is running true? The front brake calipers aren't sticking are they? Are the front rotors true? Did the same shop that check the first tire balance the second? Maybe their machine is off? Also, I had a GT that had rotors out of round and I thought it was tire shake. Turned out that the shake was coming from my rotors touching pads causing the headshake. Although, that was my GT
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