Mountain bike for sale. I've had it for two weeks. It has gears, but I don't really understand them. The right gear, number 1, is stuck and won't engage. I don't know why, I think it might be the chain because I replaced it. Also, the seat that comes with it is the original one. I installed it. I bought it for 600 (negotiable). It also has shock absorbers, which I don't understand either.