What causes handlebar shaking?

[dorkburger]

New front wheel bearings cured mine. Mine only shook if I took my hands off of the handlebars, and stopped when I put one hand back on.

[tkent02]

The high speed one is not completely harmless. The old XS 650 did it once, starting at about however fast an XS 650 will go, front wheel tracking back and forth about two or three feet very quickly, several times per second. It was very violent. Took all my strength to keep my hands on the bars. If it wasn't a wide straight road (I 5 by Camp Pendleton) could not have steered to stay on the road at all. Couldn't stop it until got down to about 35mph. Could have been caused by worn bearings, mismatched tires or anything else, this was a long time ago, maybe '76 or so.

Have never seen any GS do it, but it might if you went fast enough, or if some bearings were bad enough. Has anyone had a GS do this?

[Rob S.]

Mine only shook if I took my hands off of the handlebars, and stopped when I put one hand back on.

That describes mine. When it happened on my CB350 (with 6" longer Forks By Frank), I was surprised when someone told me it was the swing arm bushings.

"No," I said, "it's the front that's shaking."

"Swing arm bushings," he repeated.

"But it's the front," I insisted.

"Swing arm bushings," he calmly repeated.

I bought the two metal-tube things and installed them myself. Problem gone. That guy knew his sheet (or at least my CB350).

[GSXR7ED]

No Shaking

That describes mine. When it happened on my CB350 (with 6" longer Forks By Frank), I was surprised when someone told me it was the swing arm bushings.

"No," I said, "it's the front that's shaking."

"Swing arm bushings," he repeated.

"But it's the front," I insisted.

"Swing arm bushings," he calmly repeated.

I bought the two metal-tube things and installed them myself. Problem gone. That guy knew his sheet (or at least my CB350).

During my 530 trial conversion (couldn't get the sprocket hub nut off), MrBill removed the swingarm on my "T" and checked the needle bearings. They were in great shape! He greased the heck out of both sides and we put it back on once we put Bill's 630 chain he donated to me.

I haven't had any shaking in my bike so I am fortunate in that regard. My new fork brace improved stability at higher speeds but I should also check the front bearings like DB suggested.


Ed

[Carter Turk]

If the fork brace is the old hoop style, there is a possibility of misaligning the forks, as there's a little slop in the mounting holes, but then the front axle has to go through, so it might be moot.

[Guest]

The high speed one is not completely harmless. The old XS 650 did it once, starting at about however fast an XS 650 will go, front wheel tracking back and forth about two or three feet very quickly, several times per second. It was very violent. Took all my strength to keep my hands on the bars. If it wasn't a wide straight road (I 5 by Camp Pendleton) could not have steered to stay on the road at all. Couldn't stop it until got down to about 35mph. Could have been caused by worn bearings, mismatched tires or anything else, this was a long time ago, maybe '76 or so.

Have never seen any GS do it, but it might if you went fast enough, or if some bearings were bad enough. Has anyone had a GS do this?

Dang, that was the beginning of a tank slapper, those are just about impossible to recover from.

[Dogma]

...
Have never seen any GS do it, but it might if you went fast enough, or if some bearings were bad enough. Has anyone had a GS do this?

Not without first having traction interrupted. I had the rear end of my 1000G step out a couple feet once, but the ensuing oscillation damped out almost before I knew what was going on. Bwringer had a similar thing crossing a wet railroad track on his 850. The way I remember that story, it took a couple seconds to damp out. Edit: I see now you were talking about high speed. Both of these were at maybe 30-40 mph.

When I first got my 1000G, I would get some unnerving wobbles at highway speed after passing through a truck's wake. Adding a fork brace actually made it worse. That got me to examining the forks, and I realised they were binding a little. I fixed that by resetting all the triple clamps, and the wobble went away. I also had worn steering bearings at the time, but I don't think I replaced those until later.

[GSXR7ED]

Preventing Wobble

So many factors to consider:

Tires (Age, Tread, Balance, Air Pressure)
Bearings (Front Axle, Swing-arm, Rear Axle)
Triple Tree (Fork Brace)
Forks (Springs, Oil)

Thanks for all the feedback.




Ed

[Rob S.]

So many factors to consider:

Tires (Age, Tread, Balance, Air Pressure)
Bearings (Front Axle, Swing-arm, Rear Axle)
Triple Tree (Fork Brace)
Forks (Springs, Oil)

Ed

But isn't there a correct order to check things? (Most likely to be causing shaking, most likely to wear out sooner.)

Obviously, simple "external" (free) things like tire age, tread and pressure should be eliminated first. It doesn't cost anything to check the tread or adjust the pressure of tires.

[bonanzadave]

But isn't there a correct order to check things?

Mine had a head shake. I thought it was a dented front rim. You could see it. Got a whole different wheel and tire and it made no difference. Head bearings. Tighten the stem nut.

[850 Combat]

The high speed one is not completely harmless. The old XS 650 did it once, starting at about however fast an XS 650 will go, front wheel tracking back and forth about two or three feet very quickly, several times per second. It was very violent. Took all my strength to keep my hands on the bars. If it wasn't a wide straight road (I 5 by Camp Pendleton) could not have steered to stay on the road at all. Couldn't stop it until got down to about 35mph. Could have been caused by worn bearings, mismatched tires or anything else, this was a long time ago, maybe '76 or so.

Have never seen any GS do it, but it might if you went fast enough, or if some bearings were bad enough. Has anyone had a GS do this?

XS 650s were famous for it.

[GSXR7ED]

Order

But isn't there a correct order to check things? (Most likely to be causing shaking, most likely to wear out sooner.)

Obviously, simple "external" (free) things like tire age, tread and pressure should be eliminated first. It doesn't cost anything to check the tread or adjust the pressure of tires.

I would start (like you said) with tire condition/air pressure, then alignment and all that it entails. Make sure the wheel balance is good too. (That requires removing both wheels/which can be alot of work) From there, check the bearings and grease, grease, grease them if they are in good shape.

I'd also check the engine brackets and make sure the engine is tightly bolted.



Ed

[posplayr]

But isn't there a correct order to check things? (Most likely to be causing shaking, most likely to wear out sooner.)

Obviously, simple "external" (free) things like tire age, tread and pressure should be eliminated first. It doesn't cost anything to check the tread or adjust the pressure of tires.

There are intrinsic dynamics (call them modes) in motorcycles that manifest themselves in both wobble (front end shake) and weave (rear end swerve).

Depending upon a multiplicity of factors, these "modes" can damped or un-damped or grow which you can probably call the "mode character". The mode character can vary with speed and how big the disturbance is that might set it off.

The modes are always there, but the charter can change and it is many factors that can change it. If noting else, do the easy and cheap stuff and see if it gets better; it probably will until you push it harder and the mode character gets worse.

Sometime you will think it is fine and then there is something that triggers the mode and puts it into a growing character (like the losses of traction described by others).

So NO THERE IS NO SPECIFIC order, but there are is a long list of first things to check and in the end it is do it all.

[dorkburger]

I would start (like you said) with tire condition/air pressure, then alignment and all that it entails. Make sure the wheel balance is good too. (That requires removing both wheels/which can be alot of work) From there, check the bearings and grease, grease, grease them if they are in good shape.

I'd also check the engine brackets and make sure the engine is tightly bolted.



Ed

A quick note on greasing roller type bearings....Its possible to overgrease them and cause early failure due to overheating. We come across this semi regularly in hvac service when overzealous techs get crazy with the grease gun, particularly in fan/blower applications.

[tkent02]

A quick note on greasing roller type bearings....Its possible to overgrease them and cause early failure due to overheating. We come across this semi regularly in hvac service when overzealous techs get crazy with the grease gun, particularly in fan/blower applications.

You think that can happen in a stering head or swingarm bearing that only moves a little bit instead of spinning constantly?