When selecting 2nd gear, it starts to jump in and out of gear, then eventually the box locks up. I then have to rock the bike back and forth to unjam it. All other gears are fine. I bought the bike with this prob - changed selector forks and shifter drum. Any ideas??
dogs are worn on 2nd gear. did you say you changed the shift forks? While you had the motor open did you notice the dogs on the SIDES of the gears being worn at all?
They are part of the gear, there are 3 or 4 square blocks that slide into the gear next to it when the shif fork moves it. If they are rounded they will not hold into the other gear and jump out. I rode 82-83 RM250's for 10 years, went thrugh 3 transmissions. I still have one 82 250. Good luck Ed.