I took mine apart when I got it because the selector switch was missing the spring that locks it into place when you put it in position and I was determined to figure out why it wasn't working.
So basically it flicks from safe to full auto and back to safe. firing on semi vibrates the selector into full auto position. (it still does this, I'm still waiting on a part.)
Before you start monkeying with the gears (more on that in a bit) I'd suggest just removing the switches from the outside of the gun and see if maybe they're just pushed down too tight.
Be very careful that you don't lose the detent spring that allows the switch to "click" into position though... if you do that you'll be in the same boat I am with the switch that only really works in Safe and Full Auto.
That being said, The gears on my gun
were a bit misaligned and it's a HUGE pain to figure out how to re-align them since it requires some trial and error.
If you do take the plunge and try to align them yourself there... this PDF and Video combination was the most helpful thing to me for trying to figure out how to get them together again. but even with them both for reference it took me 2 and a half hours to figure it out.
The video isn't the best thing in the world and the real take away, that he doesn't really mention, is that the selector switch on one side of the gun needs to be in a specific orientation so you can rotate the other one a bit at a time...
it's almost like a ratcheting motion, moving one then the other and then back to the first one until they line up.
www.letsdesignhappytime.com/AKACR.pdfwww.youtube.com/watch?v=YlDB5Y-ncJUI literally had to take breaks in-between tinkering because I was getting incredibly frustrated trying to figure out why, even though I thought I was following the instructions, it wasn't working.