jmics, My son races and practices on the same CR125. We usually go to the track, the Sat. before the race, he probably rides 3 or 4 hrs. then races about an hour or a little more on Sunday. Sometimes we go to the track during the week. The book says change the ring every 7.5 hrs, I try to change it about every 10 to 15 hrs. Sometimes I feel like telling him he cant practice cause he;s wearing the bike out but that's why we bought it. Do you think I'm changing the ring or top end too often ? The first ring I went over 20 hrs and the engine had no compression. but still ran, I found that the ring end, or little tip at the end had broken off. I have over 30 hrs on the top end on the CR250 . Seems like the smaller the engine, the more maintenance there is.