I have an 04 zr900. And I'll tell you that it is very reliable. I'm not sure when at what mileage you would rebuild the engine. I guess that would be a personal preference. The suspension is awsome. As for the torque. it has the power when you need it. The ZR's are a performance sled. It handles great through the trails. And it will kick butt on a staight away. I realy can't give you any type of specs. I'm just letting you know from my experience with zr900. And I love it.