eli0s you are right. The problem are these sprites. But with your example I also get a gap, if the speed is 200 or above.
laoniustudio
I made a new example with only one tiledbackground, like eli0s suggested. This seems to work. I tested up to (2000*dt) without a gap.
h*t*t*p*s://drive.google.com/file/d/0B5FlDY8sggF4Tm91RFhVY3VNeE0/view?usp=sharing