Yesterday, my bike started to feel "surgy" while under load, at higher rpms.
At first I thought it was one cylinder cutting out from fuel starvation, but now I hear a knocking or clacking noise from the valve train when it happens.   It is intermittent and seems to return to normal after I up-shift or let it idle a few moments.  Just started to notice it, so it is hard to say if it's getting worse.  Seems to happen more when it is fully warmed up and I am trying to accelerate at higher rpms, maybe 7K and up.

If I ride more gently, the bike seems fine (even at high rpm) , so it doesn't seem like I've hurt anything yet...but something is not right.

It is a 94 GS500E with about 7500 miles on it and it seemed to be running fine, especially after a recent carb clean, re-jet, and tune-up.  It is filled with fresh fuel, good battery, starts and idles fine.  40 pilot and 125 mains.
Pulled the plugs and they look very good and the carb intake boots were in good shape and look ok.

The carb work was recent.  Plugs and air filter too.
I have not checked the valve shims....sounds like it might be cam chain slap or detonation, maybe, I dunno........
Any guesses or tips?  Diagnostic advice?
All help is a greatly appreciated.

Floats in the carbs are sticking? Sounds like uneven fuel level in the carb bowls giving you temporary lean mixture. Is sound really new or are you hearing regular ol' GS noises?

Sounds like detonation. Did you just add fuel or have you been on that tank for awhile?  What has been the most recent things done to the bike?  Even mundane daily stuff can cause an issue.

Thanks for the replies..

All the work I mentioned is very recent since I just got the bike last month.
I know that most likely I caused the problem and the carbs/fuel system is the likely culprit.  The noise is what scared me into posting. Maybe it is detonation.....

The noise is definitely new, but it is relatively faint and intermittent. 
I am not sure I would notice it, if the bike wasn;t acting up at the same exact time.

The full tank of fuel is new, but I got it the same place I always do.  Inside od the tank is a little rusty, but no too bad and the strainer looks clear.

I read a tip somewhere on this site that said to run the petcock in prime position and see if it clears up.  I'll try that today.
I can also check the fuel level with a clear tube from the bowl drains, if I can dig up some tubing.

I am not sure what level they are supposed to be at......I set them upside down per the manual and thought I did a good job. (hah!)

Is the fuel level supposed to be around the bowl gasket height?  Maybe I can search and find that answer.

I checked the float levels with clear tubing on the drains.  The fuel level eyeballs right to the level of the bowl gasket on both sides. Both floats seemed to operate fine when I had them apart.

I also ran it on the prime position of the rear fuel valve and it made no difference.  Still had the intermittent surges at higher rpms.  No noise that I could hear, but it was windy.

I lifted the tank and all the lines look good.  No kinks, cracks, or collapses.

I straightened the shutoff screw at the tank petcock......it was a tiny little bit off vertical and I discovered that it was actually two turns out so I turned it in a full turn and then to a perfect vertical.  I figure I turned it the wrong way when I had the tank off last time, but I don;t see it making a difference.   Maybe it will help as that is listed in the wiki for troubleshooting fuel starvation problems.  I just did that now so I'll see if it makes a difference tomorrow.

After some more searching, I guess I should clean the cap vents.  I will get on that tomorrow too.

+1 on the gas cap vent.  A clogged vent will give you this type of symptom (lean, surging, etc).  Have you ever popped the fuel cap off the bike after this condition happened?  If you did and a rush of air went into the tank, that is your culprit.  Good to clean it anyways to rule it out.

I would also do wd40 test for intake manifolds and check the exhaust too, you could have a leak in either and it would do the same thing.
Cool.
Buddha.

I agree with Buddha.  Check manifold intake.  It's the rubber part between the carbs and the engine.  If there is a microscopic crack, you have more air than gas and it's lean.  Also, these carb boots have O-Rings that collapse and get old.  Same thing.

Do the WD-40 test. If the speed increases while the engine is running, you have a leak.  I will mention that I would only buy OEM carb boots and O-Rings.  Make sure that they are tight.

Screwing with the tank petcock had no effect - the problem still shows up.

Driving all the way home with the gas cap open had no effect - the problem still shows up.

Soaking the carb boots with WD-40 had no effect on idle speed.

I do notice that after running the bike for longer periods, the hanging idle still occurs.

Quote from: step on March 22, 2012, 02:41:30 PM
Screwing with the tank petcock had no effect - the problem still shows up.

Driving all the way home with the gas cap open had no effect - the problem still shows up.

Soaking the carb boots with WD-40 had no effect on idle speed.

I do notice that after running the bike for longer periods, the hanging idle still occurs.

I noticed that my hanging idle (as slight as it may be) is only prevolent when the bike is good and warmed up.  I directed a bit of carb cleaner at the c-clip on the left side of the left carb and found my leak. I am still not sure how to seal it and still have the butterfly move freely, but I am gonna start by spooging some HD grease on there to see if that works.  Check this are for leaks too.