I need carb low-speed circuit help

[wera racer]

I'm having trouble with the idle circuit on my 2002 GS500 twin. They carbs "spit" or "hiccup" for lack of a better term while idling. I resealed the intake boots to the intakes, cleaned the carbs well, even though they look fine, and drilled out the factory brass plugs so the low-speed air screws can be adjusted. I then tried various settings with the air screws and when none of them helped, settled for the factory setting of 2.25 turns out from seated. Here's a video and if you listen closely you can hear the hiccups. Any ideas? Rick

http://s1196.photobucket.com/albums/aa414/rbartemus/gs500/?action=view&current=090510pics004.mp4

[mike-s]

sounds like it *might* be spitting back through the carbs a little. Possibly due to the timing and "one of those things" or maybe its compression related? have you done a compression test?

What imean is you'd not be getting these noises unless it was spitting back out towards the carbs, and agressive timing and leaky valves are the two ways i can think of this happening.

[wera racer]

Thanks, Mike, I'll check the compression. It pulls real strong once you put the revs to it. I did notice that, after I did all the work to the carbs and boots, it didn't start doing it until it warmed up...so maybe I need to check the valve shims, too. Many thanks! Rick