You can do a couple of things to try to bring out the original sound but you cannot fix the crack by welding or soldering or anything like that so don't even try.
First, drill small holes at the ends of the crack to prevent it from getting bigger.
Second, you can remove material along the length of the crack to stop the broken edges from rubbing against each other when you hit the cymbal. This is probably why you have a trashy sound now. You can remove the material by hand by filing along the crack with a small file. Another way is to use a drill press with a small end mill. Once you punch through the cymbal you can then move and guide the cymbal so that the end mill moves along the length of the crack. Move slowly so as not to break the end mill. Since your crack is near the bell, this might be a difficult process.
Good luck. Would love to see pics if you have them.