Trying to get text to slide accross screen: Newbie

I'm trying a very simple line of text sliding across the screen.

• I write the text.
• Go to motion in fx panel
• put text to 1 side and create a keyframe. 
• scrub timeline across to end of clip
• click 'motion' - at this point either text diappears or its clipped by something and i cant get whole line to show
• move the text to endpoint
• then when i scrub across timeliune i can see a blue outline moving with only some of the text visible. What the actual f is goung here.? It seems to be clipping the text to the frame width. 

Any suggestions gratefully received.