Brake Caliper Problem

[dunny29er]

hey guys got my new 140cc dhz and when i was assembling it i was trying to get the brake caliper to open up so i could slot the disk in i managed to get it open but it was sliding along the disk heaps and when i ride it the brake hardly stops me

 

[rach88]

I'm not 100% sure, but I'd say try bleeding your brakes for starter
YouTube - Pitbike brake bleeding