Topic: brakes

[purim9]

New member here. How are all of you?  I have a "74 cb 750 that I can't get running for a bunch of reasons. I would like to attack one problem at a time. My disc brake is stuck. I replaced the pads, and did a poor job of cleaning the piston and calipers because it is still stuck. I Replaced the pads with Organic pads. Caliper A's pad moves a little on the cotter pin and the other pad will pop out. Neither is a problem because when I bleed the brakes they are stuck to the dic again. I will take some brake cleaner and do a better job. the adjusting bolt does not seem to allow the caliper A to give the disc some clearance.  can any one help with this?

[sniper1]

Purim9,

I had a similar problem with my '77 550. the pad would not "retract" after releasing the lever, and the brakes would squeal like pigs. I messed around with the brakes for a few weeks, trying different things. There are several posts on this subject and I would research them all. I was able to fix my problem by doing two things:

1. Disassemble the caliper and clean it out very well. I had some crud in there, (not much) but may have been enough to cause problems. After removing the pad, use an aircompressor to "blow" the piston out, 30-80 lbs. should do it. Cover the end with a rag to keep the piston from shooting across the garage. Inspect the piston and cylinder and seal very well. My advice is that if the piston is in poor shape, replace it.

2. Replace the seal. This I believe was my problem. The seal is about $7 dollars (Z1, Old Bike Barn, Bike Bandit have them). The seal looked to be in good shape, but since I already had a new one, I replaced it any way.

Lube everything up according to the manual, reassemble, bleed the brakes, adjust accordingly and be on your way. If this doesn't work, my best guess would be that you have a master cylinder problem. I would go the cheap route first and trouble shoot the piston seal first though.

[MCRider]

New member here. How are all of you?  I have a "74 cb 750 that I can't get running for a bunch of reasons. I would like to attack one problem at a time. My disc brake is stuck. I replaced the pads, and did a poor job of cleaning the piston and calipers because it is still stuck. I Replaced the pads with Organic pads. Caliper A's pad moves a little on the cotter pin and the other pad will pop out. Neither is a problem because when I bleed the brakes they are stuck to the dic again. I will take some brake cleaner and do a better job. the adjusting bolt does not seem to allow the caliper A to give the disc some clearance.  can any one help with this?

Welcome. Your starting with a frustrating problem. Many of us have struggled with sticky brakes. But first a little housekeeping. Your post is perhaps better off in the SOHC/4 forum. Maybe a mod will move it.

Onwards. as to naming parts. The pad on the pin with the cotter pin is the ""B" pad. It should be a little loose in its mount. It also swings with the bracket. The adjuster bolt is to set the clearance of this B pad and the disc. About 5 thousandths. The adjuster does nothing to the A pad. When installing the A pad, you'll push it in with a lever, try not to touch the braking surface of the pads. Then install the caliper. Then pumping the brake will move the A pad to the disc. Once it touches the disc, it will take up the clearance you have set on the B pad, and the clamping action is your brake. Releasing the lever the B pad retracts from the spring on the adjuster, the A pad should retract a few thousandths. Not much but the difference between the wheel turning or not turning.

The only thing that retracts the A pad is the flex of the rectangular ORIng in the caliper itself. If the A pad doesn't retract, you'll need to remove the caliper and on the "hot" side, the side with the fluid, remove the pad, the convex plug then the piston, per sniper's post. You'll want to have a catch pan under all this to catch any fluid.

[Zaipai]

Purim9,
1. Disassemble the caliper and clean it out very well. I had some crud in there, (not much) but may have been enough to cause problems. After removing the pad, use an aircompressor to "blow" the piston out, 30-80 lbs. should do it. Cover the end with a rag to keep the piston from shooting across the garage. Inspect the piston and cylinder and seal very well. My advice is that if the piston is in poor shape, replace it.

This is probably your best bet, however if like me you don't have an air compressor handy, you can use a grease gun threaded into where the brake line goes in and pump grease into it until the it pop's out. It will make a mess but it often works. I soaked mine in transmission fluid over night first and I think that helped, however I had lots of rust in mine that you may not have.

Just an idea.

GL
.: Scott :.