Loosen the chain or belt and take it off the sprocket. Take off the cover and remove the small limit driving gear and the limit switches themselves. You will have four bolts with 5/16th heads on them holding the motor up. Remove them. This should expose the gear and sprocket assembly. You will have 3 bolts with 5/16th heads on them holding the gear and sprocket in place. Remove them and the gear and sprocket should slide right out. Put the new one in. You will have to rethread the holes in the new gear and sprocket, you just run the old bolts through and they will thread it for you. Make sure you lube the new gear and put it all back together and set the limits.

You can also just replace the gear by driving out the bottom roll pin, then drop the motor and slide the gear off. Don't worry about replacing the worm gear, bushings, or anything else.

I have a Python II opener. My problem is that when I push the opener on the wall, the door opens about 2 ft. Then I hit the button and it goes down. This happens quite frequently. It also happens with the remotes. However, some times the door will open when I keep my finger pressed on the button. Please help.

Disconnect the door from the opener in the down position and see how heavy it feels when lifting it. If it is taking alot of effort you may have a broken spring or you need to have a technician come out and adjust the spring tension. Otherwhise on the back of the unit you will have two black knobs marked up and down force. Adjust the up force a quarter turn or so and it should take care of it for you.