my midi moto has a leak and won't start??

hi, i have a midi moto, and as of a few days ago, it wont start or even tick over without the electric start being held on, even then there is no power going to the back wheel. there is also a load of grease collecting in the fairing bellow the engine and pull start, as you can see i know pretty much nothing about engines myself so can you please help... im 14 and would like to get it going again many thnx