After a long day working on it, I did it! My bullet started again after some months of inactivity. In fact I could not solve the electrical issues I had (there are still some pending... ) so today I went thoroughly through the entire wiring system and I plugged everything back as per the manual says! And guess what, after charging the battery it started!!! I have to say, I'm proud of myself! :) But still I think I burned a part of the wiring so I'm not so sure I've fixed everything! Anyway, it's already really cool!!! :)