M.H.
My suggestion would be to reward him with a prize (something on the larger side) when he goes #2 in the potty.
Here's how it went for me: My son, who will turn 3 in July, was competely trained on pee-pee by 2 1/2, but he would NEVER go #2 in the potty, no matter how much I pleaded with him. He only wore pull-ups at night, so he would either wait until he had the pull-up on and go #2 at night or he would hold it as long as he could, and then he would ask me to put a pull-up on. I would let him, becuase I wanted him to go, not hold it. Then one day, I finally refused to get a pull-up and told him he HAD to go in the potty no matter what. Instead, he figured out how to get one of his little brother's diapers out of the drawer and diapered himself!
Then about three weeks ago my mom came up with the suggestion of the reward. I don't know why I didn't think of that. Of course my son wasn't going to go #2 in the potty just becasue I was telling him too. He needed more motivation.
We bought him a special toy (nothing outrageous - a toy train for about $25) and we showed it to him in the evening (around the time he would normally ask for a pull-up). He got very excited, and then I explained that we would only open the toy if he went poo-poo in the potty. He decided he would try, but he didn't go (I think he thought just trying would get him the toy) so no toy. He was determined though, and tried again, and sat on that potty until he went. We sang the potty song (something I just made up), did the potty dance, gave him the toy and made a big deal out of it.
At bed time, we put the toy away, and told him that it was special and he could only play with it after going poo-poo in the potty. So, the next night he was excited to go #2 in the potty and get to play with his toy again. He liked the idea that it was special that way. Also, I made sure that his little brother was not allowed to play with it, so that made it even more special to him. He went on for about a week and eventually stopped asking for the toy after every poo-poo, but continued to be fully 100% potty trained since then. He has not once asked for a diaper in three weeks. He can play with the toy all the time now, and is proud of himself and even tells everyone "I'm potty trained!" We still keep a pull-up on him at night, just in case, but he ususally wakes up dry and goes right to the potty.
Also, I don't know if this makes a difference or not, but we potty trained him to go on the big potty, not a little potty chair (I think I would rather change a poopy diaper than have to clean out the potty each time).