Long story short, my fuel tank has a leak in the seam. I think I'm going to go with the soldering fix, however, I'm wondering if i need to seal the tank also with something like Red-Kote? I know the tank didn't come factory sealed (CBR 600 F3 BTW).

Thanks in advance!

 

Do both. The tank itself needs to be structurally sound then put a liner in it. The tank is first treated to remove rust and stop the oxidization process. The liner is an epoxy... you pour it in and roll the tank till it sets up... Works great. No more holes develop from the inside an no more plugged fuel filters from rust in the tank.