I was on Mt Antero last weekend at about 12000 ft coming down when my brakes went to the floor. Had to pump brake pedal four times before pedal came back. This happened twice in a short time then they worked good again. It was not a good time for this to happen. If it would have happened a few minutes earlier we would not be here. I'm going to talk to Honda about this in the morning. This is not a good thing since these do not have a emergency brake to fall back on. When this happened we had no brakes at all on a real steep grade and hairpin switchbacks with several thousand ft drop off. I'm just reporting this so hopefully everyone can be prepared if you have this happen. Will report back on this issue after I talk to Honda. Hopefully they replace master cylinder. I checked for leaks but all looked good.