Your bike has them, all the bergs have these bolts that help hold the rocker box on, they are located on either side of your spark plug.
What you are talking about here is called "axial" play, and is indeed something that you need to set, AFTER, you have put the rocker box back on. Or, if your rocker box is still on and you just want to adjust them you can.
Remove the valve adjustment covers and the place the motor at TDC ON THE COMPRESSIOIN STROKE. Now, before you begin, grab hold of the rocker arm itself and push/pull it back and forth, parallel with the rocker arm shaft. You should feel some play here. Whilst sitting on the spark plug side, you should be able to slip a .05-.01mm feeler gauge between the end of the rocker arm and the aluminum end cap piece. Check the dimension in your owners manual to be sure, but, I'm pretty sure that's what it is.
If it is out of spec, then just loosen the bolt that looks like it passes through the rocker arm shaft, which it does via a slotted hole. If the dimension is too loose simply tap on the end of the rocker arm cap, if it's too tight just wiggle the rocker arm back and forth and it will get looser. Once you have the dimension set, simply re tighten the bolt per spec. Be careful not to overtighten!!
A thorough explanation can be had by downloading the 2001 owners manual, part #3, pages 9a & 9B