Sounds like it was broken in improperly or not long enough. I would try as Gregger says and put in some nice fresh 30 wt dino oil and run it nice and warm. Gun it almost to the redline and leave it there in the lower gears for about 100 miles (no 5th gear), rev it up and down using engine braking a lot too and that should seat the rings up if that is the case. You can do a search for the "Motoman Break-in Method" and that explains this same process very well.
You could also do a valve check to see if you have a sticky one or the seat is bad.
