I have read others results here from jetting solutions/problems.  I never messed with my GS much in the jetting department.  I always thought that "Suzuki likely did it right since it is an air cooled engine... they surely wouldn't want to run it lean on us!?"  Well I think it was on the lean side on the top end.  After all these miles on this bike with me holding that throttle pinned waiting for something to happen.  I finally threw in those 125 main jets.

My first impression of the 125 main jets was not positive.  So, then I tried raising the needles with no real improvement.  This thing really likes to fall on it's face if the throttle is wacked open.  I went back to the stock main jets and was back to opening the throttle waiting for things to happen.  I then looked at DynoJets installation instructions for this bike and found that they are RESTRICTING the slide lift holes on both sides.  Sure enough, I look at those slide holes and they are the biggest I have seen.  Being the rather cheap individual that I am, I goto OSH and get some small (metal) Allen headed plugs to fit into the slide lift holes.  Installed two of them, one on each slide in the outer most hole.  This slowes down the slides reaction to throttle input.  I found this to be much better than the stock setup.  I have settled on using the 125 (one size larger than stock) main jet with the needle on the stock height.  It will still fall on it's face if the throttle is wacked open, but much better than before with more top end power (especially top gears).  If I was to play with this some more, I would be trying to restrict both of the slide lift holes rather than just plugging one of them as I have done.  I have noticed that in the lower gears the throttle response is a little poorer (1st, 2nd mainly), but the gain in the upper gears more than makes up for it.  I still need to roll on the throttle in a controlled manner at higher speeds after this mod, but with 40 odd hp on tap I guess I can't expect too much better.  Another avenue to attempt this result would be to install stiffer slide return springs, mine are stock.  Float level is also stock setting.  Idle mixture screws 2 3/4 out.  This is a stock exhaust stock air filter bike.  Pics:

the slide hole was the perfect size to tap and then install the plug, if I become unhappy with this mod I could just back out the plug, I am tempted to try and restrict both with plugs and drill 1/16 holes in them,

now thats creative good on ya, i like to see people trying new things.
do you really have a 120 on the back wheel?? that must be scary to ride on in the wet

Nice write up!  Have you installed size 40 non-bleeder type pilot jets?  Those may clear up the "falling on its face when you snap on the throttle" problem.  It's falling on its face, because it doesn't have the proper jetting to get the rpm's up there.

No, I didn't try a bigger pilot jet.

Yes, the front tire on the back rim can be challenging, but not as challenging as the too big front tire on the front.  It tends to "fall" into corners, so I have to be ready for countersteering incase it wants to fall to the ground   Other than that, I get good quality rubber on there and they are all tear offs.

I have been riding this setup for months now.  The only draw back is that it has a flat spot just off idle with no load on the engine.  So, when engaging the clutch it hesitates a little canyon carving.  Otherwise, much better than my stock setup.  This flat spot is due to the slides not opening at the off idle no load range as easily as prior.

43K - yea its got one foot in the grave - you said you decked its head, and did you put rings and hone it when it was apart if so ... you're cool then.
Anyway a modded motor can need entirely different jetting. you should jet it up till you start to see a drop in performance and then drop back one step. In any case you cant be too far off even right now. Just 1-2 points.
I'd use a plastic screw 4-40 with a phillips head and cut it flush and sand it ... instead of that metal thing. If it some how somes loose ... you'll do more damage with it.
You can also try 40 pilots. That idle flat spot may be the stock pilots.
Cool.
Srinath.

Wouldn't plugging the holes make the slides open faster? Not sure, but I bet you could go up a couple steps on the main jet and go to the 40 pilot for more power. A filter and pipe would help too. That's cool how you tried plugging the holes, now I don't have to try it, I can just wait 'tilll you find the perfect setup and copy you 
Have fun, and keep us updated 

The perfect setup in this aspect seems to be sorta vague. I dont plug them. Most bikes actually work fine without it. Suddenly one comes along that does show a definite preference. I have run back to back with plugged and unplugged and its too close on my old 89 to call.
I have also seen people need 130 mains and tussey has 142.5 - no idea how ...
plugging a hole in that slide will make it go up slower. So will adding a heavy ass steel bolt ...  in it.
DJ actually suggests closing one and blocking another. That will be disastrously slow to go up and may be needed just for their stupidly tapered needle.
Cool.
Srinath.

I did hone and put new rings in when doing the valve job a few years back.

My off idle flat spot may improve with the larger pilot jet.  I'll throw that idea around for next time I have them apart, and yes I will look for some nylon plugs to replace the metal ones I put in there (they really don't weigh all that much). 

It really is amazing how much better it rides this way.  I used to have to just about tuck in when the speeds got above 80mph, now it will pull to 100 and cruise there (upright).  I also saw close to 130 tucked in on the speedo recently (my gearing is one up in front but with lower profile rear tire).  I have had this bike since about 1998 and never really messed with the carbs.

I know I could get some more gains with a pipe and air filter.  I just don't have much planned for this bike.  I took it to a track day a few years back and parked it after half of the day, mainly due to the poor engine performance and poor suspension action.  I had an aftermarket air filter (uni foam) for a while and that really was a bad idea with the stock jetting (it also ended up dropping the bottom into the air box).  I have even tried some of the paper aftermarket replacement filters (don't remember the brand, but the opening was a little bigger than stock and it claimed to be a stock replacement) and that totally screwed up the power band.  Motorcycle engines are picky with jetting and such as seshadri_srinath has posted, same bikes can need different setups. 

......... and the most recent discovery during a recent tune-up was:  one of the carburetors was suffering from too high a float level due to both tab position and deteriorated inlet pipe O-ring; I have cured these issues and no longer have the off idle stumbling I reported earlier; fuel mileage should go up even more now;