buy a new best quality you can get cap and rotor (hard to find high quality in C and R) at worst you will have a spare C and R at best found your problem. I have had many poor quality C and R mostly Caps really. Need a known good one. As you are having trouble dialling this one in maybe start with basics make sure your timing is decent etc...I'm concerned that people get on board with carb and needle talk when you are having spark issues, keep it simple...one step at a time and all that It is odd that you are having this much trouble getting this up and running....B18 is a prettty simple beast....check your grounds as this can also create weird problems and rust will cause poor/no ground.