How do you open up the main door at Grunty Industries?

Simply do this: go were the Battery is (Hill above entrance).Then go across the moat by skiping across the poison cans. Then kill the Blue thing that bites you that lives in an anthill. Then cross to the ladder.Go up and over the ledge. You should see the train button. Press it and the train can go there now. Go to the level where chuffy is and drive into Grunty Industries. You will now be inside the Grunty Indestries building. Go to floor 1. Go to the giant door. (There will be 2 buttons, 1 on each side. One will have a picture of Banjo's head and one of kazooies). There will be a flight of stairs to your left. Go up them, and there will be a split-up pad. Split-up Banjo and Kazooie. Play as Banjo and put him on the button with his head on it, there will be small Green,yellow and red lights coming out of it. When on it press A. You should control Kazooie now. Put Kazooie on the button with her head on it. The door should open. Join Kazzoie and Banjo back together. You should be able to move in and out now. Note: Don't try to open it any other way i've tried, not possible. Hope this works, Cardkeeper.