My brothers just bought a second hand 2001 YZ426 and it seems to "jump out" of 5th gear. It happens anytime after shifting into top, it jumps out of gear resonably violently, the motor instantly free revs and then it re-engages. It continues this cycle till down shifting. Has anyone else had / heard of this problem with the 426? I've heard of problems with soft 4th gears, but it seems to me like an issue with the selector dog or pawl not holding engagement?