New Dyna with less than 2500 miles. A couple of days ago, I used the rear brakes and they just didn't release. Rode for a few minutes and they loosened up enough that I could push the bike myself. Pedal was solid so pressing it didn't do much of anything.

After a couple of blocks the disk pushes the caliper back almost enough that the pads are only rubbing lightly (and only heating up slowly) so I CAN ride it - but should not.

Rode it home slowly using only front brake. Quick inspection shows nothing wrong but piston is extended and won't retract. I gave it a gentle pry with a screwdriver but it didn't move. Swore and parked the bike for the night.

Came out this morning and the brake pedal has normal play again and the rear brake is working great. Rode for about an hour with lots of stops and starts and all went well until I stopped for a light. I released the brake and the bike kept slowing. Yep, back brake was not released again.

Before I tear my brakes apart, has anyone run into this problem on a Dyna? My gut says it would normally be pitted slider rods, but this bike is brand new. The grease is not congealed and filled with crap because it has no grease (because it's a brand new bike).

What's puzzling me is that it released overnight and worked fine for an hour.

 

Easy way to test. Carry a wrench that fits your bleeder screw. Ride the bike till the rear brakes don't release. Crack the bleeder screw. If it releases the pressure and the brakes are free, the caliper is good. Then the problem is either the flex hose is collapsed or the master cylinder piston is not returning all the way and not allowing the fluid to return to the master cylinder when you release the brake. If you open the bleeder and they don't release, you have a problem with the caliper. I know its under warranty, but at least you can tell them what you found, and you won't get the "can't duplicate" answer. Hope this helps narrow it down.

 

Great plan Greybeard. The problem did NOT happen again until I was on the ride to HD to let the mechanics have a look. In the end it turns out it was a mechanical issue: the clip on the piston was actually bent and the mechanic replaced it (no charge).


I'll remember you little trick however, it'll help with other problems as well.