I just changed the crankshaft bearings of my friends DT100, and when i assembled the engine, i`am having trouble with gear changing. When the engine is switched off, the gears work perfectly, but when idle, from first to second is impossible to shift. the gearlever seem to be stuck. When the bike is driven normally, everything works fine altough the shifting is a little bit harder than it used to be. Any suggestions of what might be the problem. thanks