I changed my 954 triple trees yesterday,b/c they where damaged from an accident. Everything was going well till today I slammed on my front break and the triple trees moved in its place. Since then every time I break it moves a little bit. I know I need to open every thing and redo whole assembly procedure, but I was wondering if you know what causes such a problem

 

head bearings!???

 

Steering head bearings. Sounds like they aren't torqued enough or they are significantly flat spotted. They are critical to steering and stability and should always be replaced as a set. If the bike was in a severe enough accident to bend the triple trees, you should probably consider replacing the steering head bearings if you haven't already..They need to be torqued just enough so that when the front wheel is raised off the ground with the steering pointed straight ahead, lightly nudging the bars to either side causes the steering to flop against the steering stop.

Steering head bearing failure is very ugly. If they fail they typically lock the steering in a single position causing a crash due to lack of steering.

 

sounds to me like the front end is no tightened down enough