determining cause of instability

[TEcklund]

Since I've been back Chef helped me get my '81 1100e back on the road.

Had some disquieting flip flop kind of front end instability.

First found the front tire air valve was loose. Tire was slowly loosing pressure. Variable one.

Loosened and re-tightened up the front and and set the steering head bearing preload. Variable two.

Felt more stable but still had an odd flip floppy side to side feel.

Swapped out the front wheel bearings. Made all the difference. Bike mileage was in the mid 20Ks. Didn't think the wheel bearings would be an issue.

Thought someone else with the same odd front end issue might benefit from this.


Next: With the valves set and the carbs balanced the vibration is much reduced. After reading over the past threads will check the engine mounting bolt clearance and determine if any shims are needed.

 

[Rob S.]

On certain old Hondas, 'head shake' frequently meant the swing arm bushings needed replacing.

 

[bwringer]

I didn't see replacing the steering stem bearings in your list.

And yeah, check the rear end; the swingarm has bearings, not bushings, and if they're bad this can feel like front end instability. Also make sure the shocks are acting evenly; springs adjusted the same, not leaking, etc.

Percentage-wise, bad steering stem bearings are much higher on the list; these WILL go bad on every GS, so that's where I'd look first.

One clear early symptom of bad steering stem bearings I usually use is instability when you're slowing for a stoplight. It feels like it's sort of "hunting" around. What's happening is that there's a notch in the steering pointing straight ahead, and it interferes with the tiny automatic corrections you make. It's most apparent when you're braking and at slow speeds.

 

[TEcklund]

I didn't see replacing the steering stem bearings in your list.

And yeah, check the rear end; the swingarm has bearings, not bushings, and if they're bad this can feel like front end instability. Also make sure the shocks are acting evenly; springs adjusted the same, not leaking, etc.

Percentage-wise, bad steering stem bearings are much higher on the list; these WILL go bad on every GS, so that's where I'd look first.

One clear early symptom of bad steering stem bearings I usually use is instability when you're slowing for a stoplight. It feels like it's sort of "hunting" around. What's happening is that there's a notch in the steering pointing straight ahead, and it interferes with the tiny automatic corrections you make. It's most apparent when you're braking and at slow speeds.

Well taken. And will certainly replace the steering head bearings at some point. In my case, once the front tire was holding air pressure and the steering head bearings were adjusted, the new front wheel bearings appeared to have solved the odd side to side flip floppy instability. The front wheel bearings weren't something I thought would be an issue with a bike with mid 20K miles.

Have a 1975 'naked' GL1000 that has a high speed head shake. Will do a tapered roller bearing swap and see if that helps. Also may go after the swing arm pivots but after I see how the new steering head bearings work out.

Old vehicles, even ones with moderate mileage, are prone to have these needs; as I'm sure the forum is well aware.

 

[Grimly]

After I rebuilt the front end I had a peculiar mid-corner feeling from time to time. I was utterly sure it was nothing at the front, not any more.
Turned out to be the swing arm bearings that finally needed a tiny bit of adjustment after many, many miles. Literally about a 1/16th turn did it.
A similar slightly vague cornering feel was usually the front wheel bearings, but not this time.

 

[Pappy]

Not your typical first post but what the heck. If I can help someone with the information then it is a great first post......
I purchased a 1982 GS550L a while back and have been getting it road worthy for my wife.
The bike, ever since I we bought it will not drive straight....at all. It "falls off" to the right constantly regardless of speed. Kind of a wallow if you will. Not a shimmy, slower like every 2 seconds.
I checked the rear tire alignment and swing arm bearings - all good. I checked the front wheel bearings - all good. I know my steering head bearings are dry and need to be serviced and thought that was the issue.
Then I found a Youtube video on aligning the front forks......bingo! That was it! Video was produced by Delboy. https://www.youtube.com/watch?v=pNEmOqY02EU
Was simple to do and absolutely took care of the issue. Hope this helps.

 

[TEcklund]

Is 'adjusting' the swing arm pivot simply tightening the swing arm attachment bolt?