I have a 98 Fat Boy that was once owned by my deceased brother. The bike has Performance Machine 4 piston calipers front and rear. A couple of months ago I noticed that the rear brakes were not feeling right, spongy. The rear brake caliper looked ok so I tried to bleed them with no difference. I decided to replace the master cylinder and it didn't help much. I pulled off the rear PM brake and replaced it with a OEM rear brake caliper. The brake finally felt firm but after riding a while I noticed that every now and then the pedal would go all the way down to the floor and then would be alright again after a couple of pumps. I checked all the lines and there is no leaking I am really scratching my head, I have been riding Harleys since the mid seventies and have never seen this before, any suggestions?

 

check the brake rotor. warping will give you that pedal/no pedal you mentioned....steve

 

Thanks Steve I will check it.

 

My rear brake started making a noise and acting funny just before the rear bearing failed. The brake was helping to hold the wheel in place...which ruined it, the axle, the belt, etc....Probably not it, but worth checking if nothing else fits as the cause...I switched my bearings to timken (all ***** makes good ones also).

 

Check the rear brake light switch. When mine started to fail a few pumps would get good break feel but it would only last a for a little while.

 

Yea what Steve said, a warped rotor will push the caliper pistons into the bore, and push the brake fluid back into the master cylinder, when you put on the brakes the piston has to come all the way back out.
Its just like when you put on new brakes and you have to pump the brakes to get the pistons pushed out to make contact.