I bought a 2001 yz426 that has been extremely well taken care of since it was new. The problem I am having, is that when it's in 4th gear under a load (even a small load like cruising down the street), and at the very top of 5th it has a strange miss. Almost like the motor completely cuts out and then comes back and repeats. We thought it was something in the gearbox, so we split the cases and tore it all the way down and inspected the gears, and they all appear to be in great shape. Also, there is absolutely no sound associated with this cut out, and 1st 2nd and 3rd pull perfectly. Im driving myself crazy trying to figure this out, and Im supposed to take it to Glamis for President's Day. Someone please help me.