Okay so Iv recently purchased my first bike the other day. It's a 2009 Gs500f

It has an issue with the idle needing adjusting which is cool, sometimes it dies while at a stop or going down the gears and slowing down fast

But today I ran into a different type of problem where the engine started dying while I was riding it. The engine would start knocking around and despite the revs being high on the tach itd stutter and die at speed. I thought the issue was related at first but after my mate talked me through it I remembered that id left the petcock on prime while letting it warm up today and it was running fine the last two days besides the idle problem.

I don't know a lot about how to use a petcock, I was told to put it horizontal (prime on my bike) to turn it off overnight so that's what iv been doing. Because the idles been set a bit low and it kept stalling with the choke on full i decided to leave it on prime when I warmed it up and it seemed to help until i rode off and it kept dying. Looked at the owners manual and it said not to leavev the petcock on prime.

My questions are
1
a)would leaving it on prime overnight and with the engine turned on while letting it warm up for 2-3 minutes idling be something that would cause the engine to stutter and die due to excess fuel in places?
b)If so what should I do now to remedy the situation

2
a) what is the go with the petcock?
b) Is there another device on my bike besides the petcock that functions as a fuel tap that will let me turn the fuel off when im not using it or is that unecessary as I was told to do?

I'm sure someone will answer this better than I, but here goes.

The action of the petcock is described pretty well here: http://wiki.gstwins.com/index.php?n=Upgrades.Petcock.  As  you can see, you no longer need to turn off the fuel supply when the engine is not running, but only use the PRI setting when the carbs are empty. So setting it to PRI overnight would do the reverse of what you intended.

As for your fuel starvation, it would appear that this petcock arrangement can cause fuel starvation because of lack of vacuum pressure (mostly on earlier models). I also have an 09, and I don't have this problem, but you could check your vacuum tube and make sure that it is delivering the vacuum as needed.

Good luck.

Yeah so there definately was a fuel starvation problem..

Turned out it had ran out of fuel 

Id checked yesterday and there was plenty so didn't even think it would be that... Should have clicked when i drove it home on reserve no problems 

Looks like Ill have to get used to no fuel gauge and filling her up after riding for any substantial amount of time Thanks for the resources on petcocks though 

There is s reserve on the petcock. You ride around in the ON position, until you feel the engine choking for gas, then turn the petcock to the reserve and get some gas.

After a while, you know the average miles until this happens.

Don't feel too bad GSL! This is how I learned when I first got my GS... thought it was a bigger problem but turns out it was low on fuel. Looking down into that tank can be deceiving !!

Now I do as HPP said... and don't forget to reset the trip counter each time you fill up so you can get an idea of how many miles you can go on a tank 'til reserve