Topic: Dragging brakes despite caliper and MC rebuild

[Mingo]

I cleaned out my caliper last week--scrapped out the seal groove with a dental pick, picked all the scaling off the seal and cleaned the caliper out. It looked pretty good. There are a few small pits on the piston, but not as bad as many I see on old posts on this forum where many posters say to keep using them.

But the braked dragged a bit. I could push the bike around the garage, but with noticeable friction.

So today I rebuilt the MC and that went well.

I also ordered a new seal from Dime City, but the seal did not fit. I'm not sure if that's my error in reading the product listing or Dime City's. The listing says fits CB 750 F/K. Mine is a 78 750K.

In any case, I ended up using the same seal, but it looks really good to me, very smooth.

Still the brakes are dragging a little.

I rode around town for about 15 minutes and stopped several times along the way to check on the disk. It was warm, but not too hot to touch. I could keep my ungloved hands on it for about 4 seconds.

So, my question is: is this just normal on these old bikes? Is there just a bit of drag all the time?

[Mingo]

Another picture

[Really?]

Did you break out the feeler gauge and adjust the screw?

[Really?]

Well, I dunno if the 77/78K has the same adjustment as the earlier models.

[steam-powered man]

the bracket that holds the caliper must be free to move, they're usually stuck/sticky.  fully disass all the parts, clean out the crud/goo and reassemble.  use a bit of grease on the shaft.  make sure the bracket can pivot freely, then install the caliper.  make sure the spring is not too tight, adjust per the manual. 

[Mingo]

the bracket that holds the caliper must be free to move, they're usually stuck/sticky.  fully disass all the parts, clean out the crud/goo and reassemble.  use a bit of grease on the shaft.  make sure the bracket can pivot freely, then install the caliper.  make sure the spring is not too tight, adjust per the manual.

I've got it as loose as can go right now. I'll look again tomorrow and see if there's any stickiness there, but I don't think so. I looked at that before I rebuild the MC.

[scottly]

Yes, there is usually a bit of drag. Prop the front wheel up off the ground, and give it a good spin; if it turns for 1/2 to 3/4 turn before stopping, it may be OK.

[Roach Carver]

Also there are two holes in the master. Make sure they are both clear.

[N30R3L0AD3D]

Not sure if this helps your situation, but my K4 had a mini puck in it causing it to lock up and drag no matter what I did. I threw it away, problem solved.

[Mingo]

Not sure if this helps your situation, but my K4 had a mini puck in it causing it to lock up and drag no matter what I did. I threw it away, problem solved.

By mini puck do you mean the plastic washer between the pad and the cylinder?

[fastbroshi]

  Yes, I'm pretty sure that's what he means.  It's there to keep the piston square on the pad I think.  If you're rolling it around in the garage and the tranny is in neutral it should roll pretty easily, the 450+ lbs not withstanding.  I think the important thing is that you oriented the seal correctly.  I believe the outside diameter edge on one side is very square and the other side is slightly rounded.  This edge is what pulls the piston back ever so slightly when you release the brake lever.  Easy to see now why the perceived slightest imperfections on the piston can affect how the brakes feel.

[Mingo]

  Yes, I'm pretty sure that's what he means.  It's there to keep the piston square on the pad I think.  If you're rolling it around in the garage and the tranny is in neutral it should roll pretty easily, the 450+ lbs not withstanding.  I think the important thing is that you oriented the seal correctly.  I believe the outside diameter edge on one side is very square and the other side is slightly rounded.  This edge is what pulls the piston back ever so slightly when you release the brake lever.  Easy to see now why the perceived slightest imperfections on the piston can affect how the brakes feel.

So, the seal has a clearly defined outside and inside ...and the outside wants to stay outside.   If I turn it inside out, it pops back into its natural position.

But are you saying that there is an up and a down orientation?  If so, which side faces the pad and which side faces the brack fluid well?

[Mingo]

Update. I put the old pads back in and the system worked. When I took them back out I noticed that the pads rattled around in the calipers--that they had some play. Then I put the new pads back in and saw that they were damn near wedged in there. So I ground the outside edges of the backing plate on the pad that abuts the cylinder.

It works.

I'll take it for a ride now and see if it holds up.