The stock Keihin carb is pretty crappy, so the Mikuni should be a plus. XR400 is really tall and kickstart only and takes a heavy boot, so if you are short of leg, they are hard to start. Once started though tons of great low end torque and power up high. They are great bikes. Super tough, beat on it all you want. Certain years have a weak countershaft. A stronger one from a later year swaps in but you gotta split the cases to do it, which is not as huge an ordeal as you would think...these are simple and straight forward to work on. Everybody goes gaga over the 600's, but the 400 is better in the tough stuff due to lighter weight.
