I recently purchased a 99 Suzuki Savage LS650 and had to do some work to get her up and running.  Everything is running great! And she is purrrring like a kitten.  However I am having 1 minor issue.  Whenever I shut off the bike, 2-3 seconds after shutdown it backfires and sounds like a gun going off!  I have been told that the bike is running to rich and I need to make it a little leaner!  Where on the carb is the screw I've also been told about that will adjust it to run a little leaner which should stop the backfire at shutdown only !  Can someone please help out a new Savage Lover/Rider/Enthusiast !!

If it runs good, don't mess with it. Check for exhaust leaks, any kind of air leak into the muffler after shutdown will make a backfire worse.

Mine give a muffled "whoomp" after shutdown. When I had an air leak.. yeah, it sounded like a gun.

Like most have said and more will tell you, the backfire is normal, also popping and backfiring on deceleration will happen also.
There are numerous posts where that issue is addressed, go to the "Tech Section" and read up on the exhaust and carb mods.....

When it matters, I avoid the occasional gunshot crack at shutdown by pulling out the choke before shutting down.