Hi I bought a baja 90 from a friend and it was cranking but it did not have a good battery so I tried to jump start it and now it's dead dead like now it wont crank or even turn on the liddle screen or lights.

 

You probably connected the battery the wrong way round and blew the main fuse. Don't know the Baja 90 but there will be a fuse in the battery pos thin wire to ignition switch. If you have connected it wrongly, you may have blown the voltage reg too, so check it is charging once you get it going.

 

Thanks