I have a deal for a 99 yz400f needing work for 800. I've heard these steel valve motors are more reliable than 250fs. I was planning on getting a 250f and I know I can handle one. But an older 400f? How would they compare to a modern day 250f in terms of power? I would be riding sand pits and a straight quad trail in the woods. Turning isn't as important as stability. However, there are jumps at this sand pits that I would like to do.