You have a bent rotor...When you move the bike the bent rotor pushes the pistons back into the caliper which causes you to have to pump the lever to get brakes again...Replace the rotor and all will be fine...has any one just changed the tire on your bike,or had the front wheel off for any reason?

 

We just replaced the tire when this started

 

I'd think U could check runout of the rotor before replacing it...

 

Sounds to me like the wheel is moving side to side. Try loosening the cap on the right side and re torque the nut on the left side to remove any play between the spacers and bearings. Then re tighten the cap.

 

If you can get the front of the bike off of the ground...Turn the wheel by hand while watching the rotor inside the brake caliper...If you see it pushing the brake pads back and forcing the piston back into the caliper...the rotor is bent.

 

a motor cycle rotor is too thin to cause a pulse in the lever, it isnt a pickup truck with a 1 1/2 thick rotor.. i just had this problem, your rotor is bent, when the bend goes thru it pushes the caliper piston in,then you have to pump the preasure back up, i just took a caresent wrench , put the bike up on a lift, turn the wheel and find the bend, bend it back, or you could get a new rotor, but im cheap/poor