Yet again my bike doesnt want to act right.  I was riding to work today and was at full throttle on the highway and topped out at 75-80 mph and it took a good 5 minutes to get to 80 and the popping is now back.  Ugh this bike has been a headache i really dont want to take it to a shop but its starting to look like i may need to. 

did a valve check 4k miles ago im going to do another one hopefully that is the issue.

What does it do if you try to ride those speeds in 5th gear? Do the problems start at the same RPM, or do they start around the same MPH, or completely different?

more details...your description is way to um... vague
what gear?
what RPM?
jetting?
pipe?
did you let budduh touch the carbs? 

I had similar problem..turned out to be tear in carb diaphragm
it was topping out at 6000 rpm 6th gear
Manoj

I have the same problem on the interstates going up hills. Bike will be cruising at 75 at 6,000 RPM in 6th gear, than will hit the hill and it will just slowly start to decelerate (with full throttle). Usually by the top of the hill I'm at 65. It's intermittent though. Some guys told me to check the ignition coils/spark plugs. I will see if new plugs do the trick.

Sorry for the lack of info.  I was very angry at the time of posting cause i thought i had fixed the problem.  I may have caused it myself by putting a inline fuel filter on the bike which might be the cause of my problem.  Lets see, i was in 6th gear at about 6k rpms and it doesn't go much higher.  Fuel throttle in 5th gear bumps the rpms up more of course but still have the lack in power and tops out at about 80.  I replaced my fuel line due to the fact that i accidentally ruined my old one putting the inline filter on.  Now i read that its gravity fed and maybe the cause of my issues.  I'm going to try to top it off today and see if i get better performance due the the extra gas weight.  If no change ill pull the filter back off, though i already spotted crud in the filter after just one day of use...

If you noticed some gunk in the filter, does your tank have any rust in it? Some of that may of ended up in the carb's and could be giving you some performance issues. Are the plugs in good shape? Might want to check the float height. If set to low it could be lean at top end. Have you gone through the carb's lately?

i just replaced the plug, and cleaned the carbs and jets.  I have to get some hose to check the float height.

The plugs you took out. Were they white looking(lean condition), black (fouled) or a nice shade of grey.

plugs showed no unusual combustion.  I remembered that i didn't engage my gear all the way a few times when i was having fun in the twisties and over revved past 11k id say a good 4-5 times since my last valve adjustment.  The best way to describe what is happening is this.  Its like trying to ride without letting the bike warm up and for some reason the bike ALWAYS misses without a pop at 45 mph no matter what gear that i am in.  I hope that helps some cause i think ive check everything else out besides carb syncing and valve clearance...

It's amazing what a good carb synching will do...

Does it hesitate (too lean)?

Or, surge (too rich)?

How many miles since the last valve adjustment?

my bike has been experiencing fuel starving past 80/85...it splutters to 100
I recently changed the fuel line,used 1/4 inch ..is this the recommended size for GS
and installed inline fuel filter on both fuel and reserve line
would any of these changes cause fuel starvation other than petcock
and which direction the arrow of the filter(Autozone ) should be facing

Manoj

it hesitates.  It seems too lean.  Someone that went riding with me suggested i sync the carbs as well.  Do you think this is the problem?  I wouldnt hurt to check.  Wheres a place to get a decent carb syncing tool btw?  Its been 5-6k miles since last valve adjustment i made a mistake before heh.  Bad memory i have it written down for a reason lol

ok i think ive been making a huge mistake this whole time.  The large screw between the carbs is only to adjust the idle and not the fuel air ratio correct?  Then i have not messed with the air/fuel in the carbs at all and i feel like a moron if thats the issue.  That is if my bike is running lean...  If someone could point out where the screws are, i think i have a idea but i dont want to mess with them if they are not. I apologize to everyone thats been helping me.

That knob only affects the idol.  The mixture screws are under a brass cap on the underside of the carbs.

any tips on removing the brass cap?

paraphrased from the wiki: drill it, work a screw into it and pull it out.

http://www.angelfire.com/mt2/mikesgs500/rejetting/

pictures! =]

they are removed, everything back together warming up at the moment... Now for adjusting. =D

havingf the worsdt time trying to adjust these where they are