My Go-Kart wont start?

I have this really nice go-kart. It has worked perfectly in the past. I have not used it since before christmas, so like about 4-5 months i have not used it, because it was cold and snowy. It was in the garage. But now it will not start. There is enough gas and the battery is fine. The lights turn on, so there is an electic flow. When you turn the key it tries to start making a reving nose and nothing else. It seems like there is no spark to start it at all. I do not know what to do. I really want this to work. Can you please help me on what i should do to try to get the go-kart to work? Thanks a lot.