78 Front wheel sticking using front brake........

[T2rminator]

Hi.
Need some guidance / advice on this, bought a caliper for the bike, new pads, new flexi-hose and steel pipe............ the front wheel sticks when front brake is applied.have bled the brake and no issues there.............. the pad returns to the caliper if i take the caliper off and put it into a vice ( yes have stripped caliper down cleaned it with abrasive and reinstalled it)the caliper pad returns ok, re installed it still not change.... once.... the extension bracket now moves where as before it didnt but doesnt make a difference even after adjusting the screw for the freewheeling.......... only thing i can think of is the master cylinder ? any ideas???????

 

[Mitremike]

A number of years ago I had the same issue on my 73. Rebulit the caliper and flush and bled-no improvement. Tore down the master cylinder and rebuilt that. Problem solved. It turned out to be stiff seals in the MC and fresh ones freed it right up. No problem since.

 

[Marty]

I would check your run out on the disk and rim as one could be bent causing a sticking problem also. Was this bike working fine in your possession before you changed the caliper?

 

[tommycarl]

I would loosen the bleed screw... if the caliper piston backs off, I'd suspect the master cylinder. If it doesn't back off, I'd remove the caliper piston and pay particular attention to cleaning the groove for the piston seal. Crud builds up in the groove and it needs to be clean to function properly.

Since you indicate that it takes a vice to push the piston back in, and I assume there are no visible issues with the piston or caliper, the seal groove cleanliness seems suspect.