I just bought a used GY 150 Yamoto, new to the whole dirt bike gig. It does not want to start. It will start for a second idle then die. There is 3 settings on the choke up middle and down. where should it be to start it cold. if i cant get it started should i look at the spark plug... any ideas would help

Thanks

 

Up is full choke, middle is half chocke, down is no choke,
Full choke to start ,then when the engine is warm push chock down in the off position.