Front disk brake(s) sticking- where to start toubleshooting?

Compensating port.Do you know about these?
-There is a wee small hole in the bottom of the M/C,that goes into the hydraulic circuit. That's how the brake fluid gets into the lines. This port has another purpose. As the pads wear the piston continuously moves out of it's bore, dragging the fluid with it, all the way from the M/C. And it has another purpose; Every time you step on the brake, the fluid is forced into the system at one end, and at the other end the pistons are forced out. Well, it works backwards too.When the pedal returns to it's parking spot, that fluid returns to the M/C;all but a wee tiny smidgen that is compensating for the worn pads. That's how it's supposed to work.
-Now, if it should happen that the fluid did not or could not return to the M/C, what do you think might happen?And what would be the symptom? That's right; the brakeS;plural, would stay on, and things would heat up.Now the guys talked about other stuff, which are all valid helps.Especially if the M/C cover was not sealed. But,I just wanna talk about this. You cannot diagnose a non-functioning C-port, if the pistons are hanging up, or the piston seals are not retracting, or a hose is checking.(Well you can but you have to crack open the system.)So what to do? Easy.If ALL the brakes are stuck on, it's almost guaranteed to be the C-port. If just one sticks, it ain't the C-port.Or at least extremely unlikely.
-Now what to do about it. Well guys already mentioned about cracking bleeders. This will let the fluid go somewhere and it's business as usual until the very next application;when they stick on again.And if they are all stuck on, you can crack any bleeder and they will all release. It's that easy.
-So you wanna fix it.Well that port is as far to the back as it can be in the pressure chamber, so that as soon as the brake pedal moves,it closes the port and begins the braking action.If the pedal does not park where it is supposed to, or if the pushrod that connects the pedal to the piston is too long, then the piston inside the M/C will also not return to its parked position and it will fail to open the port. Did you get that?Read it again.These two stops have to be synchronized.
-Easy check. Having proved all brakes are sticking on(or at least both fronts), and therefore that the C-port is not opening,here is what to do. Get the front wheels into the air, and get the brakes locked.Then loosen the M/C from its mount and move it towards the rad. That will allow the piston inside to move to its stop,and open the port, releasing the brakes. Shazzam!
-But perchance it does not release the brakes, then the port could be plugged. How to prove it? With the M/C still loose, crack the line going to the front wheels. If the brakes release, there you have it; the port is plugged. Be it debris, or rust or an incorrectly parked piston; that would be for you to determine.
-But let's say it did release right away, as you loosened the mounts.That would indicate that the pushrod is incorrectly seated in the M/C piston,or incorrectly adjusted.Fix it.
-Now I couldof told you just to loosen the M/C in my opening statement, but you wouldn't have learned a single thing except what size wrench to use.Plus now every person that reads this post between now and eternity, will learn a little bit about brakes too.
- 'course your problem might not be at all related to the Cport, but in less than 5 minutes you can prove it and hardly get dirty, cuz you don't really need to jack it up.
Awrighty then, beer-break!