Worst part is the mainspring - it takes less than four pounds pull to bring it to full cock. Sparks OK but not enough force to completely open the frizzen, therefore it might set off the prime, but most often not.
Any suggestions for a 'smith in Minnesota who might replace the mainspring for me?
I just corrected that problem last night, on a CVA plains rifle. In my case the frizzen cam was too long, and it also needed polishing as well as the top surface of the frizzen spring.
In your case, since it's a POS anyway, you might try a DIY application. Any blacksmith can harden the spring for you, just have the smith heat it to cherry red, and then quench in 120 degree Canola Oil. After that it will be brittle. So you need to temper it.
For a knife I know folks that put the steel in an "oven", heating to 400-500 degrees, then air cool, and they do it twice, but that will probably still leave you a brittle spring. I was shown that a gun spring can be tempered by submerging in melted lead, which begins melts at 625° but for running ball it is closer to 700°.
So in the demonstration that I saw, the fellow attached a piece of copper wire to the spring so he could retrieve the spring, and then submerged the spring into the melted lead. He let it sit for about 10 minutes, and when he removed it, the lead didn't cling to the spring..., he removed it, then grabbed the end that was for the screw (this spring was held in place by a screw) with a pair of pliers, and tapped the pliers against the lead pot to get the lead to shake free. Then he let it air cool.
It seemed to have worked, as it didn't snap when he tried it in a lock. NO IDEA if this guy was "lucky" or if he had come up with a way for person without much tech to temper a gun spring.... but since you need to replace the part anyway, maybe you want to give it a try?
LD