I'm having this problem on a go kart with the 110cc chinese engine. The cdi box looks like the pic you posted. I checked all the wires like you said and everything seems to be good. I have already replaced the cdi and still have no power coming from the cdi to the coil. The cdi i bought is supposed to be a performance cdi and looks different than the original but still has the same plug in. It also has a green led light on it that does not ever light up. Could my new cdi just be bad?

 

Just because the CDI is new doesn't mean it is good. I bought several from the same dealer and they were bad. I had also bought several from another dealer and I was just lucky to have tried one of his which is still good and working. I went through a lot of CDIs before I got "lucky". After I got it running I went through the remaining CDIs and threw away the new ones that wouldn't work. Lynn Edwards walked me through the ordeal and I can not say enough good things about him. He gives expert advice for free and he does in a way that a person can understand. Again let me say, I bought 6 or 7 new CDIs that were bad. I also bought 3 or 4 new ones from a different dealer that are all still good.