not sure if yer new to the site, but if so....welcome aboard!!! a model number would be of great help for answers to your question, as it could be just unburnt fuel/oil dripping from a thru-hub exhaust ( 2 stroke) or actual gear oil leaking from a seal. a quick test would be to smell it.....does it smell like exhaust, or does it have the nasty odour of gear oil?