Hello! 'nene' means boys, it's like the masculine for child. We have also 'nena' for girls :)
Motochorro is an Argentinian made up word, with two roots: Moto for motorcycle, and Chorro, which is a robber or a thief (notice this is slang, chorro is used mostly in the sens of waterjet: chorro de agua).
So, those are thieves in motorcycle, you can see them here trying with the wrong guy...
https://www.youtube.com/watch?v=yvy440TY1Sw
They often steal cars while they are driving, stopping close to an attractive one when the traffic light is red, and the guy who's not driving would break the window of pillion for example, and pick up the a wallet or a purse.
Take care,
Alejo.
REF.: I'm a Spanish Teacher (and also Argentinian ;)