[fbr]

Bob, Do not split the cases yet. I had a very similar sounding problem with one of our '07 CRF250R's and this bike shares many parts with the CR125. The Drum Shifter is recessed inside the end of the Shift Drum Center. It engages the shift drum with two sping loaded plungers that keep outward pressure on two pawls. On our bike, one of the plungers was stuck in the hole that it is supposed to slide in and out of. The plunger spring was fully compressed and so there was no spring pressure on the one of the pawls. The tansmission would not shift in that direction, only in the other direction using the pawl that was functioning normally. I popped the plunger back out and everything worked fine. I reassembled everything a couple of times after some deburring and so forth but the problem reoccured until I replaced the spring, plunger, pawl and, I can't find the receipt to verify, but, I think I replaced the Drum Shifter also. This would be the part that has the two holes that the plungers and springs sit in.