What is the fastest 4 stroke dirt bike?

My best guess is for a stock dirt bike, the BMW HP2 Enduro. It puts out 105 hp at 7000 rpm. The following is a excerpt from a 10 day test of the bike by motorcyclists-online.com:

The HP2 is a true gravel rocket and the ultra strong engine is good for some indecent top speeds off-road. It can easily do 125mph, truly a break neck speed off road.

If were talking pure mx bike, KX500 or CR500.