High speed wobble?

[DimitriT]

Hey folks,

I finally got my 1982 GS550L on the road again and it's running strong after some engine work.

Yesterday I rode it hard for a few minutes, taking it near 80 mph for several miles. Once it approached that speed I noticed the steering became a little mushy and it started a slow side to side wobble. I carefully let up and it returned to its normal tracking.

One thing I did recently was take some of the preload off the rear springs. Hard to imagine that could cause a problem.

I have progressive shocks (rather old ones) in the rear and progressive springs in the forks with a bit extra preload. I also had a Givi topcase mounted in the back, although there wasn't much in it.

I know the upright seating on the L model is not really intended for higher speeds but I just want to know what its limits are. The motor still had plenty more to give.

 

[bonanzadave]

BTDT for the last 20 years. Ive tried virtually everything to fix it. You mention it....Ive done it ! I finally figured it out.....DONT GO OVER 80MPH !

 

[Guest]

A fork brace helped on my 1000G, with the caveat that if not done correctly it can certainly make it worse. Also, not sure if one exists for that model.

 

[Guest]

I recommend a bit more experimentation:
1. recreate the problem, without any changes
2. add preload to the rear shocks, try to recreate the problem, and see if anything changes. Then remove the preload, to get back to your baseline.
3. recreate the problem, and when it's wobbling, slide your weight back on the seat, then up on the tank. Does the wobble change either way?

Also:
a. check your steering head bearings; shouldn't be too tight or too loose
b. check your rear swingarm pivot bolt tightness

 

[motorush]

Install a steering dampner. The road it self, concrete with grooves etc.

 

[grcamna2]

Have you tried removing the top case to see if that could be causing your speed wobble ?

 

[Guest]

My 750 wobbles at those speeds. I assume it's the narrow tires and wind buffeting on my fairing. I think these bikes were made before center of mass was really thought about much. Top heavy on a narrow footprint at speed sounds like a recipe for a little wandering to me.

 

[Sandy]

A fast weave or wobble generally initiated from a problem with the front forks and suspension while sliw weaves are generally a sign of something not right in the rear. Could a bad tire, worn swingarm bearing, bad shocks or wrong settings etc. First I'd do is remove the top box. Even though it's empty the wind buffeting off it could be triggering the weave.

 

[Big T]

Narrow tires?
My 78 runs true to over 100 without a wiggle
The cause is a mismatch between the front and rear suspension

 

[steve murdoch]

As Sandy mentioned a bad or worn tire could be the cause.
Also check the air pressures.
Improper air pressure even in a new tire can also be the cause of a head-shake/wobble.

 

[bonanzadave]

Ive tried virtually everything to fix it.

For the first 10 years Ive had my bike I could roll the throttle and watch the phone poles go by in a blur. Then the weave started. I replaced everything mentioned and then some. Tiresshocksbearingsbushingsspringsetc.....all combinations of pressures preload dampening and alignments. Still weaves.

 

[wyly]

I've learned to keep both hands on the bars at all speeds on my 84 GS1150. I've heard criticism of my other ride a 79CBX for sketchy handling and it was somewhat true, but nothing like I've had on my GSX.

 

[Guest]

That's kinda why I keep this GS. After having a late model bike and feeling the difference, riding the GS is a walk on the wild side.

Which reminds me, I used to have a ZX1400. Had it toured out too. Really nice Givi side bags and a trunk. Biggest I could find to mount on it. In hindsight I don't know why I didn't just get a concours. Anyway, one day on my way to work I got on an entrance to the highway I had taken a thousand times. It was a big circle. I had been incrementally taking it faster and faster every day. All of a sudden one day right at the exit of the circle onto the highway the bike bucked me off. I was doing about 55 and somersaulted for about fifty yards down the onramp while the bike slid on it's side into the middle of the two lanes. I managed to get up and pick up the bike and get it to the cement barrier in the very middle and that's when I realized my wrist was broken. That accident screwed my back for the rest of life. I was very lucky I didn't land infront of someone comming around the corner. I still don't understand why the bike suddenly tank slapped and bucked me up in the air. It was one of two things; 1. I hit a stone I didn't see because it felt like the bike hopped into the lean, or 2. all that luggage had upset the balance of the bike and the way I took that turn was the limit it could keep it's composure before showing me I was stupid.
before

 

[Guest]

"All of a sudden one day right at the exit of the circle onto the highway the bike bucked me off"

Sounds like you highsided. As you exited the circle you were probably accelerating while still leaned over and lost rear end traction, until it caught again and threw you off. Could have hit a small oil/anti-freeze or water patch, maybe your tires weren't as warm as on previous days, etc. Can happen for many reasons, been there done that.

 

[roeme]

Huh, I've generally experienced my 550's as quite stable; and I've pushed them up to 180km/h (111mph). And it must be said, I've discovered serious repairs on one of them (welds on triple tree; welds on the frame).

That being said; I had some icky situations with all of my bikes; but it always came down on suspension issues or worn tires.

Oh, you're referring to an L...less preload on rear...eh, maybe this reduced front downforce just enough to make it iffy

 

[DimitriT]

Huh, I've generally experienced my 550's as quite stable; and I've pushed them up to 180km/h (111mph). And it must be said, I've discovered serious repairs on one of them (welds on triple tree; welds on the frame).

That being said; I had some icky situations with all of my bikes; but it always came down on suspension issues or worn tires.

Oh, you're referring to an L...less preload on rear...eh, maybe this reduced front downforce just enough to make it iffy

That's what I'm thinking. With the big Givi topcase on the back and the no preload, could be it was on the verge of lifting the front wheel.