Man what a great site!  I was doing some reading on the hose hookup from the tank to the pet chicken and mine was not only reversed but hooked up wrong on the pet chicken   The vacuum hose was also not even hooked up to the pet chicken .  I couldn't believe it.  The guy I bought it from said he just had the carbs gone through by a mechanic.   Sounds like he got the shaft on his service.  Anyway got all hoses hooked back up and took her for a spin.  No more backfiring and in the cold weather here seemed to run pretty good.  Before I had to use Pri all the time now it is on like it is supposed to be:)

I am guessing the vacuum hose on the petcock opens a valve of some sort and allows the gas to be sucked into the carb.  

I also think I am missing the fuel screws on both carbs:(.  I need to pull them off to verify.  I know on my mx bike I can just loosen the boots up and spin the carbs enough to adjust the fuel screw.  Can you do the same on the gs?

Again great site!

Bates

No the carbs on the GS are bolted together so you can't spin them like you can on a single.  You could look under with an angled mirror to check, but it wouldn't run real well without the fuel screws so they are prolly there.

they are there, but they are covered by brass plugs in the USA, unless someone took them out already. to remove, purchase the smallest easy-out and follow instructions, if you have a power drill. otherwise, your dealer will probably do it for a few bucks...be careful not to drill very far though, just enough to start the extractor...the screw heads are very close to the bottom of the brass plugs...

I looked up in there and it looked like I could see threads.  I will have to take another look just to be sure.