When going at it pretty good I get a pretty bad wobble at high speeds, above 80 mph.  Im not really sure what the deal is, I completly rebuilt my bike over the winter and must have something messed up.  My fork seals are leaking, is it possible that the level is lower in one then the other messing up the balance?  Also I put new neck bearings in the neck, and they are almost too good, is it possible to have the steering so smooth that it would induce a high speed wobble.

might be, but there is a whole list of stuff that can cause the wobble or "handlebar shake" Tire pressure and wheel alignment being the bigest culprit when i dealt with em. Lack of a forkbrace for my 82gs750 was another, week springs in my katana 600.

Is your front tire balanced?  Some shops just pop on a tire, put a little wieght across from the valve stem and send it out.

i dont ballence my tires at all, never did, if it vibrated that bad i unbeaded the tire and turned it 180* on the rim and that generaly solved the vibration.  my xj did wobble alittle as the steering bearings had a flat spot.

mine wobbles real bad in wind when accelerating, i just accept it, Its sorta scrary but ohwell.  But then again its when I passing in the left and am on this one uneven road.

oh ya my tire is balanced too.  And my forks are fine too

Just accept? Great until you loose control of it and spill
Try fixing it, or taking it to the dealer.  You should have full control over your bike at all times, it should be straight and smooth.

And why are you doig 80?  You're breaking the law you know...

Check tire pressure first.

I assume it didn't do this BEFORE you did the work?  

As said earlier, are ALL the wheels aligned?

Tire pressure, fork seals, fork oil level, proper fork sag.

My tire as been balanced the old school way, spin until you determine the area that needs the weight.  I dont have any vibrations so it must be somewhat close.  I might have to look into some things, I also changed the rear shock so my geometry might be off or something.  

80 is when I first notice the wobbling, it seems to get worse as I go faster, and when it is windy.  I spose if I dont find nothing out of the ordinary then maybe Ill have a good excuse to keep it under 80.

That's it, that's what I wanted to say, "steering geometry". In stock form, at rest, the bike has a 26 degree rake and 3.7 inches of trail. A R6 has a rake of 24 and also 3.7 in of trail, making for a twitchy bike. Note, that I stated 'at rest'; when you get on your bike the suspension compresses, changing your rake and trail numbers. Trail is what gives you stability, and rake is what gives you trail. So if you, change your rear shock to a longer one without changing dogbones, you have changed your rake.

It sounds to me like something is loose in the main steering stem bearing and/or the swing arm pivot bearing. You need to really check for sloppiness in these areas. Is the steering neutral? I can take both hands off the bars and the bike runs absolutely straight. If it doesn't, the rear wheel is out of alignment. Also be sure the wheel bearings are slop-free.

most of the time you have to run 80 or else youll get run over.

there is nothing rong with your bike,your gs is a light bike.  90% of all light bikes that hallass will wobel a little at high speed.

sorry about my bad spelling.

weight will only effect how much you feel it, in the frame or on the bars, its not the cause nor an eliminating factor of wobble.  Susspension (springs,oil,bushings) Bearings (steering,swingarm,wheel) fork brace/forks twisted. Tire pressures and allignments  older frames Flexed abit more in corners making them wobble.  

my GS has no bar weigts, i have aluminum clipons, i dont ballence my wheels at all. ive got a home made fairing that everyone i ride with says causes wobble when wind hits, ive got katana 600rear shock really preloaded for my weight 280 now, front forks are raised in the clamps and preloaded, all the things aside from worn out bearings/bushings that would help lend to a wobble and the only times ive ever had the slittest hint of a wobble with the GS is with Low tire pressure and Missaligned rear wheel. my XJ650 has flat spots in steering bearings so it will wobble alittle.
my katana 600 wobbled alittle untill i changed fork springs and oil then it went away.

GP 125 bikes have Far less mass/weight then the GS and if ridden like a GS wouldnt wobble for a bet ( <---sarcasim) even ridden hard you see lowsides and highsides, seldom do you see wobbles just come out of the blue going down a straight.

so can we please Not blame weight? specialy being as i out weigh most of you and carry stuff on back and i will still feel a wobble If certen things are not right, Weight having nothing to do with it.  Bar ends, lead shot in bars, this kills vibration and may slow the wobble abit, but it just masks it, doesnt stop the reason its happening

My guess ... your tires ... rear especially ... or rear shock ... my 89 felt rock solid ... so did the new 89, but been on bikes that did wobble ... I thought rear tires or rear shock were to blame.
Cool.
Srinath.

It could be the rear wheel, Ive got a B4 wheel on there now so maybe thats slightly out of alignment or something.  When I let go of the bike going say 35 mph. it will go nice and straight with no bar shake at all.  Over the winter I changed so many things so it might take awhile to figure out which one is the culprit, my bearings should be good though, but worth a check any how, maybe something went wrong along the rebuild.

Yeah, check the tightness on the steering head collars. Other than that at 80mph you have a very small contact patch, which may allow the 'shimmy', but it is allowed because something else is wrong. What is your sag set at?

<---- B400 rear wheel as well and run both 150 and 160 on it, alignment is alittle more critical but nothing extrordinary