BMX power and stamina

Hi I'm after some info on power/sprint training for Bmx I have a race meet in about 7 weeks which will involve 8 motos on day one and two motos and 2 finals on day 2. There is about 10-15 mins between two races then 20 minutes the another two races with the 10min again. Most meets have about 5 races total and 15minutes apart. I am looking at improving my sprinting speed so I am looking for advice on weight and fittness training to help in these areas.
Thanks in advance Jona