Motorcycle Repair: 1992 CBR 600 problems, maintnence, petcock

Question
Chris,
I bought a 92 Cbr 600 about two weeks ago and I am having some problems. When Im cruising along on flat ground or downhill, anywhere that I have the throttle in one spot, the bike starts to sputter/surge, and continues to sputter when I roll on the throttle, but I open it up and it seems to go away for a bit. At times the bike has actually died after the sputter. It almost seems as if it is running out of gas, but there is plenty. The bike idles fine, and this does not happen at any particular rpm range, and it doesnt happen right away either, it usually starts about 1/2 hr to 45 min into a ride. The few times it has died on me when this happened, I pulled off, made sure I had enough gas and it started right back up and I took off, however the problem was still there (the sputtering). My gas cap is slightly damaged, don't know if that could cause this. Also, upon inspection I noticed a valve off the back end of my petcock that isn't hooked up to anything. Maybe this is a venting problem? Would that cuase constant problems, or would it build up like I have described? The previous owner claimed to have had major maintnence done 5k ago. It has been sugegsted that I have my valves adjust and carbs cleaned/synced, but I can't help but think that it is something else since it does not orrur constantly... Well, thanks in advance for any suggestions you might have.  

Answer
Hi Scott.
 That line from the back end of the petcock, if it is the small hose, should go to the number 4 cylinder.  It attatches to the small metal tube that protrudes from the manifold.  It actuates the fuel valve, which is vacuum actuated.

 If that doesn't fix the problem, then you should do the valves and carb synch, which should be done anyway, as they are due.

Let me know what you find.
Good luck.
FALCON