You can totally teach him to ring a bell, but at 14 weeks he just can't hold it unless he *has* to in a crate. You need to keep him on a leash or don't take your eyes off of him when you are home. Try setting a timer for every 30 minutes to take him out. At 14 weeks he really does need to go out that often. Slowly you can try extending the time between potty breaks. At this age his body isn't giving him any warning that he needs to go -definitely not enough for him to let you know and wait for you to let him out. It's a better idea just to keep him empty
I have tellbells on my website if you're interested. Others on here make hanging bells. It's great to teach him now, but don't expect much for another month or two!