The newer bikes use dot 4.It absorbs water.If you wash your bike alot or ride in alot of rain this is where the problem lyes.Dot 5 is much better to me because it does not do this but has less brake feel than dot 4.

 

On the way to Sturgis, My bike did just that.
Was told "Altitude" with some air in the lines= BO BRAKES.
Thought it was just me, I was wrong. One other bike in our group did the same thing after a trip through the Rockies. At the dealer 6 other bikes. Bleed and flush them!

 

When brakes overheat in can cause the pads to glaze, decreasing their performance.

 

Although this is true, but this would not lead to loss of pedal as the op described, you would still have a hard pedal.

 

Use your FRONT BRAKES!
less effort for the amount of braking you get.
Problem solved.
Just watched two riders crash because they panicked and used only their rear brakes and skidded.

 

Almost definitely boiled fluid. Once cooled, the pedal will recover most of it's effectiveness, but it's important to flush out that fluid and re-bleed the system.

 

Down shift my Son and keep the RPM's up..........

 

I used to do some road racing(4 wheel) and this sounds like boiled fluid as others have said. Switch to Motul 600+, it's great stuff.

 

thanks from a flat lander.we dont ride in the mountains much so we learned something.we will flush front and rear brakes tonight.thanks for your help.

 

This is a scary thread...If you aren't familiar with your braking system...Take it to someone that knows what they are doing...Never mix dot 4 and dot 5 brake fluids as they are not compatible.