http://www.youtube.com/watch?v=jW8hMGm23zk

This is my first gs so I'm not sure if this sound is normal. Instead of just letting it be, I figured I'd double check with some of the fine folks here on gstwins. A little background: I did a valve adjustment and opened up the right exhaust. After that, my floats were flooding and gas would just pour into the airbox when the bike was in prime. I had to clean the carbs to get the bike to start again, but now the idle just doesn't feel right. I think it should be smoother and more balanced than it is now.

When I'm sitting on the bike, I can feel a shockwave each time the a cylinder fires. Last time I checked the sparkplugs, they were coated in black and my fuel mileage is poor (~35 mpg). This makes me suspect the bike is running rich. I haven't messed with the jetting (though I'm not sure if the PO did).

Any ideas what could be going on? Maybe I just need to readjust the float height to let less gas sit in the bowl? Maybe the float airvent is slightly clogged (I have to blow very forcefully before any air goes through the vent hose).

Carbs need synchronization. Mine was just the same, but after synchro job all went fine

I tried to sync the carbs, but I may have done a shoddy job. The haynes recommends you sync at 1750 rpm on a warm engine, but by the time I got my tubes attached the engine had cooled down. I synced while the rpms were around 1200. I'll try it again with a little pep so I can sync it before the engine cools off.

The rev up and rev down sounds right to me. The idle sounds a bit.... odd. Then again, anything less than studio quality audio can make even a perfectly sounding engine sound a bit off when recorded and played back.

2005 GS500F with around 2,000 miles.
For comparison: https://picasaweb.google.com/lh/photo/u5MuufBskJD0qP3tLw9T5fMv92Tb7QwH8WLWHf8NsK8?feat=directlink

IDK. that sounds exactly like mine, idle and all.