Is the thumb nut supposed to turn after tightening lever itself,i tryed the lever many times the nut still turns ? Is this normal?i got a radrunner this weekend with some damages in box around front forks!!
Tighten the thumbnut and the lever enough that you have to use some force to fully close the lever. After that the nut should not turn by hand. If it does then there is another problem.
The inside of the nut ( and sometimes the outside of the fork) is knurled so a loose nut should rotate with regular clicks of the protrusions.
Two possibilities:
1. The nut is malformed and smooth on the inside. - demand a new one.
2. You accidentally added a washer and defeated the knurling - remove the washer and try again.