First, im sorry that title isn't as clear as it should be, but i have no idea what could be wrong with it.
Uploaded a video showing whats happening:
https://www.youtube.com/watch?v=uFz6WPUn1a4&feature=youtu.beIt was running for an hour before making this video, because when its cold it dies instantly i touch gas thingie (throttle? no idea how its called) and when its warm enough after some little Brum-brums it starts to spin the wheel for few seconds then dies again.
I'm sorry, i dont really know how to explain it, so i made a video.
If you have any ideas what is wrong please tell me, i can google it out if you're no in the mood to write long posts, just give me part names or something that could help.
Thanks!