Are the helper springs you see advertised at F&T and others big enough for a #4 long spring? I believe they say they are for 1 1/2 and 2 size longsprings. Thinking a #3 spring would be a better helper spring for a #4? Anybody have any experience adding helper springs to #4 size traps?

correct,,theyre for #2 and smaller traps. easier to put a pipe in a vice, slip the spring end over the pipe, and give it a sharp rap with a hammer on the bend in the spring. usually the easiest fix for the larger long springs. hope this helps. go easy to start with, so you dont over-do the bending.

I put1.5 longspring springs in my 3N’s and it made them plenty stout. Drilled the springs and pop riveted in.

I don’t see any “helper” springs on their site? What’s up with a “helper” spring?

It makes a weak trap strong again. You just double up the old spring with the new "Helper" spring and you have a strong spring on that side again. Some guys drill and rivet them in place. It done mostly on smaller #1's longsprings that are really old and weak. But you can do both sides on a #4 if you can find springs strong enough to add to the weaker stock springs.

I guess there’s not replacement springs readily available for some of these smaller traps? The old traps I bought at garage sales and stuff, I just replaced the spring.