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Author Topic: Head shake on my DR  (Read 568 times)

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Online Robin Brown

Head shake on my DR
« on: January 23, 2012, 08:02:11 am »
Please all in the know comment on the head shake on my DR.
Suddenly when travelling in a straight line from 100 upwards the steering starts to wiggle and gets quite violent. Slack off the throttle and it goes away.
No where near a tank slapper but feels if it is heading that way.
Accelerate back up to over 100 and all is stable. But suddenly for no reason the wiggle again starts.
Bike has done 30 000 km, has progressive springs in the front forks and I run a Desert on the front.
When the wind is extremely calm (seldom in the Cape) the bike remains far more stable.
On dirt no problem.
I am now going to try and balance the front wheel again.
Any comments very welcome
 

Offline DirtHound

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Re: Head shake on my DR
« Reply #1 on: January 23, 2012, 08:06:01 am »
What's the tyre pressure like?
Previous bikes: '81 XR500;   CBR400 NC23;   '85 XR600;   '97 VTR1000;   '91 KDX200;   '85 XR600;   '97 XR600   :paw:
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PE to Cape Town on the XR  |  XR Pigfest  |  Anniversary ride - Old Houw Hoek Pass
 

Online Robin Brown

Re: Head shake on my DR
« Reply #2 on: January 23, 2012, 08:12:44 am »
I have tried everything from 1.2 bar to 2 bar
 

Offline DirtHound

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Re: Head shake on my DR
« Reply #3 on: January 23, 2012, 08:16:42 am »
Steering stem bearings perhaps?
Previous bikes: '81 XR500;   CBR400 NC23;   '85 XR600;   '97 VTR1000;   '91 KDX200;   '85 XR600;   '97 XR600   :paw:
Current:  '01 XR650R; '06 CTX200
PE to Cape Town on the XR  |  XR Pigfest  |  Anniversary ride - Old Houw Hoek Pass
 

theotherguy

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Re: Head shake on my DR
« Reply #4 on: January 23, 2012, 08:23:25 am »
jacket buffeting in the wind...
 

Offline Snafu

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Re: Head shake on my DR
« Reply #5 on: January 23, 2012, 08:39:24 am »
Robin

I after riding behind you yesterday, i really for for you. It did not look comfortable at all. I think it mostly happen around 120km/h.

You have a new Desert on the front. Did it also happen with the previous tyre?

Theotherguy has a good point though. I have seen it happen before.
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Offline grego

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Re: Head shake on my DR
« Reply #6 on: January 23, 2012, 08:53:27 am »
could be your suspension settings... have you tried cranking up your rear preload a bit?

here's an interesting article from cape-enduro about suspension setup... http://www.cape-enduro.co.za/forum/viewtopic.php?f=7&t=6641
 

Offline volroom

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Re: Head shake on my DR
« Reply #7 on: January 23, 2012, 09:26:43 am »
new front tyre?
I had a friend that put a MX tyre up front and had that exact same experience. Changed the tyre and all good. some MX tyres says not for highway use...for a reason
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Offline MildDog

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Re: Head shake on my DR
« Reply #8 on: January 23, 2012, 09:46:32 am »
I had the same thing on my DR.

Tire pressure is the first check, you've done that.

Try hardening back suspension? Or take it to someone who knows (Superfoxi is a good option)

If you've just put a new tire on it may be that. Certain tread combinations cause head shake (I think).
I crash test all of my safety gear. Do you?
 

Offline lecap

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Re: Head shake on my DR
« Reply #9 on: January 23, 2012, 10:36:06 am »
To check (in this particular order):
Tyre pressures. The DR should be stable at anything above 1.4 bar front. To get decent service life out of your tyres you should run 1.7 bar f & r and go up to 2 bar with the rear if you've got half the household on the back or do highway speed.
Knobblies should be run harder on tar than dual purpose tyres but that's more to make them last a bit longer.

Steering head bearings & wheel bearings.
Both will be close to perishing at your mileage. The original steering head due to lack of grease on assembly. The wheel bearings are only sealed on the outside and moisture will by now have turned the grease into margarine and caused corrosion & wear.

The DR650SE is not prone to develop high speed wobble and I would say the Wilbers springs rather make the bike more stable.
As long as the rear shock is not fitted with a spring much stiffer than OEM or the preload adjusted way over the max. allowed setup I don't think the rear suspension setup has the potential to cause the problem.
BTW high speed wobble will typically be caused by too much rear spring preload which increases (steepens) the steering head angle, reducing front wheel trail and inherent stability.

Very aggressive MX patterns do have the potential to cause high speed stability issues. If you have ruled out all other possibilities you might have to find other tyres or slow down. (Volroom is right).

Also try to stick to a combination of tyres with the same oer similar characteristics front and rear. (as in the same pattern or combos like Bridgestone TW41 / 42). Handling problems are one point, different grip on tar / dirt or especially on wet tar are another one. A wildly over- or understeering bike is neither fun nor safe to ride :-\
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Offline Operator

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Re: Head shake on my DR
« Reply #10 on: January 23, 2012, 10:52:16 am »
When I bought my DRZ it had the standard "Grippy" something tyre on front and a Dunlop D606 at the back.
The D606 was about 60% worn as I bought the bike secondhand.

Whenever I went over 110 the head started to shake and with the increasing speed it became
worse.
I tried everything, tyre pressures, balancing the front wheel, setting the suspension harder/softer etc................nothing worked.

I was frustrated and ran out of ideas.  Everybody that was knowledgeable gave input and nothing
worked.


Then I replaced the backtyre...............and viola !!!
The headshake was gone. Just like that !!

Rode the bike another 15 000km before I sold it in December and never again did I have
that problem.
Weird.
« Last Edit: January 23, 2012, 11:17:30 pm by Operator »
 

Offline Crossed-up

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Re: Head shake on my DR
« Reply #11 on: January 23, 2012, 11:15:38 am »
I had a similar prroblem with my XT.  The bike came with a "mostly tar" 140 Maxxis DS tyre.  The shake was terrible and only went away when I changed that tyre.  The choice of front tyre seemed to have little effect.
 

Offline superfoxi

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Re: Head shake on my DR
« Reply #12 on: January 23, 2012, 11:44:41 am »
The Desert front is one of the worst tyres for road use...
I put one onto my old XR many years ago and took it off again after the first ride. It was OK on dirt but on tar it was almost unridable.
 

Offline Hagar

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Re: Head shake on my DR
« Reply #13 on: January 24, 2012, 05:11:27 am »
Feel if your back wheel has some play.  Grab it at the front and back and try to wiggle it.  I recently discovered mine had developed play, and after replacing the wheel bearings the mild wandering I had from 130 up, went away.  Remember that water crossings..
 

Offline lecap

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Re: Head shake on my DR
« Reply #14 on: January 24, 2012, 09:08:13 am »
Head bearings are not so lekker any more means it looks like a combination of a not ideal tyre and a head bearing issue.
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Online Robin Brown

Re: Head shake on my DR
« Reply #15 on: January 29, 2012, 06:04:22 pm »
Thank you to all who responded. I took off the Desert changed the front tyre to a T63 and then rode a 900km recce into the karoo. The bike is now a completely different animal. No shake, totally controllable and great to ride. Superfoxi had the answer.