Topic: Front Disk Brake Locked Up

[cphlegar]

My 77 750 has been sitting in 100 degree heat and humidity for a week or two without being ridden and my front disk brakes are now locked up. Don't know if the heat has anything to do with it. Haven't worked on the brakes previously so not sure where to begin. Any ideas?

Chris in Houston

[strynboen]

its that littel return hole in main cilender..if it not are free..the pressure builds up..when the oil gets varm

[Gordon]

Haven't worked on the brakes previously so not sure where to begin. Any ideas?

That's the problem right there.  Unless you know for a FACT that the brake caliper has been cleaned and rebuilt recently by somebody you know and trust, then doing so is one of the first things anybody should do to an old bike after they purchase it, IMO.  Look in the Brake FAQ.

[thorbito]

I recently purchased my '76 CB750 and the front brake has been binding, not locking.  I can still push the bike in neutral.  After Googling it, it seems to be a pretty common ailment.  That's the bad news.  Let us know if rebuilding yours helped.

[crazypj]

They all do that sir. 
 You need a thin wire to clean out holes in master cylinder (around 0.010"), check pivot is moving free (probably not?) check pads are free in caliper

[KingCustomCycles.com]

The most common problem I see with sticking, other than the things mentioned above, is corrosion build-up behind the caliper piston seal and gobs of corrosion in the bore where the piston resides. Remove the caliper, press the piston out with a grease gun and homemade fitting, clean thoroughly, some would replace the seal, I don't usually, and reassemble with a touch of grease around the puck and piston.  Now that wasn't so hard, was it?