I take it from the name that a Sun Jet is a Chinese import?  My son owned a Chinese scooter and I can tell you that the electrics are a little "fragile".  Assuming that the new battery is both charged and not defective, you could have caused a break in one of the cables + or - when you disconnected them.  I had to run new earths from the battery and the engine on my son's scooter. 
Also as Perry says, the fuse is a good place to start with diagnostics.
Cheers
                
 westcountry
                
 October 2013