What is the cause of hands off,headshake

What is the cause of hands off, deceleration, intensity increasing headshake? I thought it was tires as I replaced mine and it just about went away, but then after another set of identical tires it came back.

I aligned the wheels with a laser to be spot on with no effect. I think I might introduce a misalignment to see if it changes .

My bike does this too, has since new. As I recall, in the past different tires, stopped it for a while. It does it now a bit with not new K-81's. It will not do it at speeds over about 30mph. The slightest touch on one of the bar ends will stop it instantly though so I have quit obsessing over it. I asked myself the very logical question "Just when is it necessary to ride 'hands off' anyway?".

Biscuit said:

.........so I have quit obsessing over it. I asked myself the very logical question "Just when is it necessary to ride 'hands off' anyway?".

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I agree, however I think its a indication that something is wrong. No modern bikes do it.

Ball bearings with no way to preload.

Tire pressure and wheel alignment.

I think the key wood here is "modern" bikes. I don't think anything is actually 'wrong'. Could it have been engineered out back in the day? Probably. It could probably be re-engineered out of our bikes today too. I think it may have something to do with the isolastics. Perhaps as the tire kicks a bit do to road irregularities the iso's move a bit amplifying that movement and causing the shakes felt at low speeds. It just take such a light touch on the bars to stop though I don't think it's an issue.
I can just picture this scenario when the Commando was in production. Test riders mention the low speed, hands-off shake and the engineers say "so what, what kind of an idiot rides with no hands anyway?" Of course this was before 'stuntahs'.

concours said:

Ball bearings with no way to preload.

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wheels or steering head? A person could take a few thousands off the spacers to preload them a little.

While not considered "modern" by today's standards, my '84 H0nd4 Nighthawk S ( a fairly competent canyon carver) did the same thing. Two different front tires, three different rears; same thing. The Norton does the same, right around 30 MPH. And, as noted earlier, any pressure or weight on the bars makes it completely disappear. I have other things to worry about at the moment...

Nathan

My FJ1100 does it anytime.

My '02 sv650 would do it after the tires had some miles on them.

Adding preload to the steering head bearings to stop it also makes the bike feel like there is bag of cement setting on the back. Jim

I bought five Commandos brand new in the 1970s, they all, every one, would head shake.

Take your hands off the bar and notice your body immediately move to the right in a reflexive effort to counterbalance the bike going left.

Perfectly set ISO, doesn't matter.

The drive side, the left side, of Commandos are heavier than the right side with the primary, both chains, clutch, etc , all being on the left.

Don't take your hands off the bars and all will be fine.

Most infmaous for head shake is state of both tires but mostly rear I found. All cycles oscillate forks to some degree to stay upright automatically but more so the slow one goes Anything with normal slack life isolastics or worn like swing arm spindle fit will aggravate/accelerate the shake to crash if not grabbing bars back. My factory evethying Trixie with new tires with 2 lb less in front was hands off stable down to 30 mph beforee it started to wibble forks but not bad untill 20 mph. As her rear worn it would onset at 45 mph. Let go at time to deal with jacket zip or yellow jacket in helmet. Only Peel with rump rod link did not wiggle-shake forks to almost walking speed even with about bald rear and slab sided front. Play with higher air pressure and difference between tires to see the effects but likely have to fit new tire to isolate other factors. This little wiggle is actually going on constantly to some degree but not noticed with hands on UNLESS accelerating nicely in long-ish held sweeper, ALL HELL can break loose aka THE Hinge. Stiff fork bearings will aggravate/magnify this as I discovered on a old Honda someone asked me to ride to help figure out its wild broncho onset below hwy speed that stopped with new stem bearings. Oh yeah Peel w/o rump rod, so only head and breast steady would onset heat shake under 20 mph, until rump rod hooked back up then hands off like bikcycle to walking speed. Do check the shock mounts on swing arm are still nice and from. Other things are chains too loose so the flap tugs on other slacknesses in clutch to swing arm to front iso gap into forks. Jacket open to flap in wind or cover on cargo coming off or slow tire leaks...

jimbo said:

concours said:

Ball bearings with no way to preload.

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wheels or steering head? A person could take a few thousands off the spacers to preload them a little.

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You COULD do that, BUT because they are garden variety ball bearings, not angular contact or tapered roller, they are not supposed to be set up like that. YMMV :idea:

concours said:

jimbo said:

concours said:

Ball bearings with no way to preload.

Click to expand...

wheels or steering head? A person could take a few thousands off the spacers to preload them a little.

Click to expand...

You COULD do that, BUT because they are garden variety ball bearings, not angular contact or tapered roller, they are not supposed to be set up like that. YMMV :idea:

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You might have to upgrade to deep groove type ball bearings, they can take some thrust loads

jimbo said:

You might have to upgrade to deep groove type ball bearings, they can take some thrust loads

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The standard 6205 2RS bearings should already be "deep-groove". :shock:

What is the cause of hands off, deceleration, intensity increasing headshake?

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Taking both hands off the bars

And don't forget the swing arm spindle.

What is the cause of hands off, deceleration, intensity increasing headshake?


Taking both hands off the bars

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beautiful, the perfect answer!

My BMW R100RS does this. Both hands on the bars at 30 mph is fine, but with one hand it shakes. I have literally tried everything to stop it happening, all to no avail. Years ago my SOHC 750 Hondas did it, as did lots of other bikes of that era. Just something we have to live with I suppose.

Bob Trigg once said in an interview that a motorcycle is two casters; the first is the trail of the front wheel and the second is the rear wheel following the front. He also said that any single-track two-wheeled vehicle can be made to wobble. So apparently the inherent stability of the two casters can be easily upset by various inputs. Tires are probably the top cause of headshake. Norton Commandos have relatively relaxed front end geometry; 27-28 degrees of rake and 4" of trail more or less, a least compared to more modern machines, which have very steep rake and a bit less trail. The easier a motorcycle responds to steering input, the easier it is to upset the stability. For examples of this stability, check out videos of riderless machines continuing on their paths until waning momentum causes them to fall to one side or the other.

Mine did it until I fitted 2.5" x 19" rims with Avon 100/90 Roadriders. Then, it only had the very faintest movement. And I mean, faint.