Hesitates at highway speed

[gsmetal]

I'm having a problem with hesitation at highway speeds.

This is for a 93 GS500. I'll be doing 60 MPH and have it in 5th gear and I get a case of the herky-jerkys.

I've cleaned the carbs (I'm running stock airbox and exhaust) and I've even taken it in for service - $200.00 later - and still have this problem. 

The dealer says they checked & cleaned the carbs, and cleaned out a layer of rust in the tank. I've had a good relationship with these guys so I believe they did the work they said they did.

The bike does idle and run better then when I brought it in but only slightly. Top gear is the only time I'm having this promblem otherwise the bike has smooth steady power in all other gears even under fast acceleration.

Has anyone else experienced this problem and can maybe shed some light on what's going on?

Thanks in advance.

[Mk1inCali]

How long ago were the valves checked/adjusted?

Does it do the same thing at the same engine speed in 4th gear?  What happens if you run 80mph in 6th?

[NiceGuysFinishLast]

Fuel starvation. Run on prime, see if you get the same issue.

[ben2go]

Fuel starvation. Run on prime, see if you get the same issue.

I second that.

[gsmetal]

Well I did try to run the petcock on PRI and I get the same result.

I'm wondering if the filter screen (inside the tank) on the petcock isn't filled with crap.

Speculation?

[slowinthestraights]

Well I did try to run the petcock on PRI and I get the same result.

I'm wondering if the filter screen (inside the tank) on the petcock isn't filled with crap.

Speculation?

Well then open the cap and look in there with a flashlight.. left side.