What Kato steam would this be? The Mikado?
The problem (at least in that case) is that the Mikado is geared way too fast.
Any loco that is geared fast requires the motor to run at very low speed to get
a good loco speed that isn't up in the slot-car region. The problem with that is
that it requires a lot more torque from the motor. As you go up hills, you have
to increase the voltage to the motor to keep up with the heavy load on it, and when
you go down hill, all the load comes off, so the motor speeds up.
If you are using DCC with BEMF, that can help. But you still have the problem that with
such a high gear ratio, a downhill train is more like "freewheeling". Thing about how it
feels to go downhill on a 10-speed bike when you are in a lower gear vs a higher gear,
or how your car feels coasting down a steep hill in "D" vs when you put it in "L".
I don't know that there is much you can do about it. This is one of the many reasons I am
such a big fan of extra gearheads when I remotor engines. They add an extra 4:1 reduction
in the gears, which obviously helps low-speed operation, but it also evens out
the up/down hill speed and the speed around curves, because the motor load is so drastically
reduced and because a train cannot "run away" down a hill so easily.
