Sticking front brakes

Hello list, my 2003 St1300 has developed sticking front brakes. I have new Master Cylinder, Rebuilt Calipers, New brake hoses up front. I recently
changed my front and rear pads with OEM pads. No issues at all after about a month after riding when I took a long 6 hour ride and I noticed the front brakes starting to bind both calipers.

From working on many other bikes I understand that front sticking brakes are a symptom of fluid not returning to the system. From my CX500 Turbo that did this to me once. The little hole that returns fluid in the MC gets stuck with grit and causes this.

Can I get some advise as what to check on the ST1300 that can be stopping fluid to return to the brake system please.

I guess the first question to ask would be "Did you bleed your entire braking system according to the procedures in the workshop manual or the ones on this site that describe the proper methods for brake bleeding?" Whether you have ABS or not the brakes are still linked and must be properly bled.

https://www.st-owners.com/forums/showthread.php?135125-ST1300-Brakes-Avoiding-the-Pitfalls

The Pressure just releases, when U ease off the Lever, and the Calipers just float away from the Discs a couple thousandths of an inch, ready for the next application.
Don't think there's any RETURN of fluid anywhere. Possibly a VERY slight amt. back into the Master Cyl. I would start there.
Also, what was the reason for the Overhaul? & How were they working before U tore the System apart ?

ESB said:

The Pressure just releases, when U ease off the Lever, and the Calipers just float away from the Discs a couple thousandths of an inch, ready for the next application.
Don't think there's any RETURN of fluid anywhere. Possibly a VERY slight amt. back into the Master Cyl. I would start there.
Also, what was the reason for the Overhaul? & How were they working before U tore the System apart ?

Click to expand...

I bought the bike used and bike had stood for 3 years. Brakes were really bad. After my overhaul brakes have been great until this problem. I just checked and
and pistons move back slightly.

Air in the system can expand with heat, and bind the brakes. Did you do a complete brake system bleed per the manual?

There is a return path!!! The little orifice at the bottom of the master cylinder covered by the deflection spoon is the return path. Yes, it can become blocked and cause pressure to build up in the system. I have experienced this very thing in the clutch circuit in another bike and know first hand the symptoms.
To remedy, remove the little spoon guarding the orifice, insert a small wire and attempt to dislodge the obstruction. Be very careful not to expose yourself to a jet stream of brake fluid if the pressure is still built up. Might want to put on some safety glasses! After inserting the wire, put some very mild pressure on the brake lever and check to see if you get a return stream when the lever is released. If you get the release stream of fluid, you have successfully cleared the return path.