My experience with these bells is that they loose volume because the solenoid armature does not return all the way, so on the next power shot there is very little travel of the hammer and it does not hit very hard. Try lifting the rear of your tender about an inch and see if this helps. That will help the armature slide back inside the solenoid coil.
In my experience the worst ones are bells which got oiled. The best I have been able to do is clean all the moving parts so they are absolutely clean. This includes the armature and the sliding points and rotation points on the frame. Even this only helps some. This bell is just crying for a conical spring around the solenoid armature. But the bell frame is all staked together, and I have not wanted to tear one apart to try this. I may try a coil spring to pull the solenoid all the way back out, but not yet.
These bells sound really good if you can get them to work properly, but I have yet to succeed at this. It is hard to believe that Lionel made this same bell for so many years, but never got it quite right.
