mcguyver was right, the switch contacts were all gunged up. I cleaned them off slowly with a dremel wire weel, and it seems to be good now.
But, I hooked up the battery and the motor with everything still apart to make sure that it worked and when set to semi the motor runs as long as the trigger is held down, is this normal? Shouldn't it just spin for a second?
Also, I dont think I got it put back together properly. Details:
http://airsoftcanada.com/showthread.php?t=31053