My XR400 is getting heavier and heavier feel on single track trails. I will be in the market for a new bike that has a lighter handling and reliable bike. How does WR450 compare to XR400. 1. Handling (lighter feel) 2. Reliability 3. How much maintenance do I have to do? 4. Torque in hill climbs 5. What is the maximum horsepower? 6. Valve issues? or any other issues? 7. How is the 1st and 2nd gear? Is it snappy? 8. How is the bike on tight cliff side single track trails? I would appreciate all your opinions.