What causes head shake
Elite HDF Member
Joined: Nov 2010
Posts: 3,846
Likes: 171
From: Simi Valley, CA
With a Touring bike what you are experiencing is quite common and while tires, suspension, and other chasis adjustments contribute, I'd venture to say the biggest influence is simply the nature of the beast with its rubber mounted drive train which includes the rear wheel.
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
that little dip causes a whole lot of stuff to happen, compression and rebound of the suspension, a momentary change in rack and trail...how you handle it- stiffening up now that you know it's there.
a front end may be settled by braking slightly- which puts more weight on the front wheel--- whether this is appropriate for the bike speed road surface traction etc is up you.
there is no harm in doing a front end fall-away test if you suspect worn bearings-- bearings are worn most by misadjusted pre load or lack of lube.
in most cases the bikes are capable of more than we the rider ask of it- trust the machine
mike
a front end may be settled by braking slightly- which puts more weight on the front wheel--- whether this is appropriate for the bike speed road surface traction etc is up you.
there is no harm in doing a front end fall-away test if you suspect worn bearings-- bearings are worn most by misadjusted pre load or lack of lube.
in most cases the bikes are capable of more than we the rider ask of it- trust the machine
mike
Outstanding HDF Member
Joined: Jan 2010
Posts: 2,916
Likes: 31
From: earth
All the things you mentioned contrubute, that dip in the pavement that started it suggests either the front and rear suspension are very different firm wise, or more likely the rear swingarm/engine dampers need firmed up with some Sta-Bo bushings. Then there is also the limitation of the machine, even set up perfect with all best components, there is a point where the 900 lb motorcyle loses its handling manners.
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Tourer
Joined: Jun 2011
Posts: 417
Likes: 3
From: Watauga, TX
This wasn't the typical pre 09 frame hinge/wallow that the old frame was plagued with. The back end was planted and sure footed throughout. This was all front end. I do need to pull the front end and add about 1/4" preload to the front end, and also change the fork oil from 10wt to 5 wt amsoil. I'm probably a month away from getting around to doing it though. I'll do a fall away while I'm at it. The bearings are lubed well, but I haven't checked bearing preload so that could be it. Tire pressure was about 4 lb low 32 lb, I normally run at 36lb front, it has a very slow leak. Its been that low and lower many times and not went into head shake. This is actually the second time the bike has reacted this way and both times have been after suspension compression/rebound. The first time was under hard acceleration and hitting a good bump in the road. This time was under steady throttle.
Outstanding HDF Member
Joined: Jan 2010
Posts: 2,916
Likes: 31
From: earth
This wasn't the typical pre 09 frame hinge/wallow that the old frame was plagued with. The back end was planted and sure footed throughout. This was all front end. I do need to pull the front end and add about 1/4" preload to the front end, and also change the fork oil from 10wt to 5 wt amsoil. I'm probably a month away from getting around to doing it though. I'll do a fall away while I'm at it. The bearings are lubed well, but I haven't checked bearing preload so that could be it. Tire pressure was about 4 lb low 32 lb, I normally run at 36lb front, it has a very slow leak. Its been that low and lower many times and not went into head shake. This is actually the second time the bike has reacted this way and both times have been after suspension compression/rebound. The first time was under hard acceleration and hitting a good bump in the road. This time was under steady throttle.
Tourer
Joined: Nov 2010
Posts: 365
Likes: 9
From: KENTUCKY
All great mechanical info above.To answer your question about on or off the gas etc...once you pick your line your throttle should be rolled open evenly, smoothly,and CONSTANTLY throughout the remainder of the turn. I am paraphrasing Keith Code. You mentioned this happening after compression and rebound...make sure there is always light rider input on the handle bars ...if you are tight on the bars and a rigid upper body you will make a wobble way worse. If you are doing this you are fighting the bike. As mentioned before trust the bike and let it do it's job, it really wants to do the right thing if we let it
However, this "relaxing" takes practice because when the pucker factor starts relaxation is the first thing to go!
However, this "relaxing" takes practice because when the pucker factor starts relaxation is the first thing to go!
Road Captain
Joined: May 2012
Posts: 561
Likes: 1
From: South Central, Pennsylvania
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