DT_mak

My first bike, dt 125 r, and I can't even get the steering lock to work. I'm gonna contact the guy I got it off but first I thought I'd try here. I turn the bars to the right and revealed is what i assume is the steering lock. I pull the slider back, put the key in, and its not turning. (It is the right key fits well ) I thought maybe i had to get a precise angle with the turning bars so I tried all positions and it still wont turn they key, is it me or the bike?? Anyone with any knowledge of how to help would be appreciated. Thanks alot Also any tried n tested good portable security devices for the bike? I've stripped alot of typical dt parts off the bike to make it look more like a crosser so theers no room for a box to carry with....cheers