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Author Topic: CB750-Front Brake Dragging.  (Read 21969 times)

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Offline Magpie

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Re: CB750-Front Brake Dragging.
« Reply #25 on: January 31, 2011, 03:16:22 pm »
Do you think aligning the front forks may help? As per:

You might need to align the front forks, but first, check to make sure you got the front axle & nut on the right way (some other post here noted they got the nut on the wrong side, an old error I've even forgotten, but common...). Also, make sure the axle caps (on the ends of the forks) are installed properly. They should be flat and even at the back side with a (parallel) gap on the front side. Tighten the rear sides first, then the fronts. The caps are DIRECTIONAL: they have a HI and LOW side to them. The gap side must be in front.

To align: loosen the lower fork clamp (triple tree) bolts just enough to be loose, then finger-tighten them. The top ones should be tight, as per normal, so the tubes don't slip up during this next part. Loosen the bolts to finger-tight on one side of the fork brace (usually the non-brake side is easier). The next step is easier with a friend standing by with a wrench: get on the bike, on both wheels, and pump hard down & up several times on the front end. Try to hold it down on the last "bounce" (just don't let it all the way up), then have your friend tighten the lower triple tree bolts. Then let up and tighten the fork brace. This relieves little stresses all over, providing your tubes are straight.
 Could it be that the disk may be slightly out of align?
Cliff.
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Offline Silverback

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Re: CB750-Front Brake Dragging.
« Reply #26 on: January 31, 2011, 03:56:32 pm »
Just an update to why my brake was dragging/sticking. I pulled the caliper off this weekend and found that the pad itself was sticking in the bore. I recently bought this bike, and apparently it had sat a while at some point. So, the contact area between the pad and bore of the caliper had a good deal of corrosion/gunk in there preventing the pad from moving more than a mm or so. I cleaned this area thoroughly and made sure the pad could move in and out freely. The piston was in pristine condition, as well as the seal. I assembled with a bit of silicon grease in the suspect area and lubed the pivot arm well. Took it for a long spin (it was a warm 45 degrees) and the brake does not drag at all and the squealing is gone (for now). Might be worth an afternoon to look into.
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Offline Magpie

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Re: CB750-Front Brake Dragging.
« Reply #27 on: January 31, 2011, 06:03:15 pm »
Today I split the caliper and removed the pads, cleaned up the edges, pushed the piston back in the caliper, and readjusted the arm. I'm using stock Honda pads which have not been painted. It's not dragging in a straight line but does a bit when the bars are turned so the next step is have a friend come over to help align the forks. Further reports to follow. Cheers, Cliff.
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Offline Spanner 1

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Re: CB750-Front Brake Dragging.
« Reply #28 on: January 31, 2011, 06:26:17 pm »
I think it's wear in your front wheel bearings ( wouldn't take much ) allowing the wheel to 'cant' when you turn the wheel to either side and thus causing the brake rotor to lean a fraction and so rub against both pads..... rather than the fork legs ' turning' out of alignment, very little rotational force on the legs by turning the steering IMO and forks are fixed by the mudguard bracket... dunno.
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Offline MCRider

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Re: CB750-Front Brake Dragging.
« Reply #29 on: January 31, 2011, 06:32:13 pm »
Quote from: Spanner 1 on January 31, 2011, 06:26:17 pm
I think it's wear in your front wheel bearings ( wouldn't take much ) allowing the wheel to 'cant' when you turn the wheel to either side and thus causing the brake rotor to lean a fraction and so rub against both pads..... rather than the fork legs ' turning' out of alignment, very little rotational force on the legs by turning the steering IMO and forks are fixed by the mudguard bracket... dunno.
That sounds "more right" to me. I would be suspicious of the wheel bearings if the brake feel changes when you turn the fork side to side. How else could the wheel cant in the fork, being held at the axle? Perhaps the fork, but seems to me...

If they've never been changed, now may be the time anyway.  :)
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Offline Magpie

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Re: CB750-Front Brake Dragging.
« Reply #30 on: January 31, 2011, 07:34:13 pm »
Thanks but I don't think it's the bearings because they are new, new spokes and rim, new fender, new TT100 tire, rebuilt forks, new steering head bearings, new piston and seal in the caliper, rebuilt master cylinder (I cleaned the return hole again), frame is straight and true. It has about 9.5 miles on it.
 I'll do the fork alignment and report the results. Must get beer to entice friend over to help. Drink AFTER helping.  ;D
Cliff.
« Last Edit: January 31, 2011, 07:35:57 pm by Magpie »
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Offline MCRider

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Re: CB750-Front Brake Dragging.
« Reply #31 on: January 31, 2011, 08:13:53 pm »
Quote from: Magpie on January 31, 2011, 07:34:13 pm
Thanks but I don't think it's the bearings because they are new, new spokes and rim, new fender, new TT100 tire, rebuilt forks, new steering head bearings, new piston and seal in the caliper, rebuilt master cylinder (I cleaned the return hole again), frame is straight and true. It has about 9.5 miles on it.
 I'll do the fork alignment and report the results. Must get beer to entice friend over to help. Drink AFTER helping.  ;D
Cliff.
Yup guess its the forks. Ditto on the beer, hold till after (if possible  :) )
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Offline Magpie

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Re: CB750-Front Brake Dragging.
« Reply #32 on: February 01, 2011, 03:51:56 pm »
The fork alignment seemed to help as well as pumping the tires to specs. Now to let it sit for a bit and see what happens.  Unfortunately no beers were injured in the process. Cheers, Cliff.
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Offline Magpie

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Re: CB750-Front Brake Dragging.
« Reply #33 on: March 27, 2011, 10:46:14 pm »
Well, I moved the bike and the brake is dragging again. After much messing about it came down to the passive puck, not the one that moves with the brake lever, that has been dragging. I can see the piston move back when the brake is released and there is a gap between the brake puck and the rotor when it's at rest. I've back off the adjustment screw until it's loose and that seems to help. I looked at aftermarket pads and they are thicker than the new Honda ones so those didn't go in. The brake arm is loose and moves well so it's not holding it in position. I wonder if the long spring is not pushing against the caliper hard enough to push the passive pad away from the rotor a bit more? Maybe it needs some miles put on the pads to wear them down a bit.
I'll let it sit a bit and see what happens in a couple of days.
Cliff.
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Offline Magpie

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Re: CB750-Front Brake Dragging.
« Reply #34 on: April 03, 2011, 05:17:53 pm »
So it's sat for a few days and if I turn the bars hard right there's no drag, hard left it drags. Maybe I have to do the alignent again?
Cliff.
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Offline scottly

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Re: CB750-Front Brake Dragging.
« Reply #35 on: April 03, 2011, 07:25:05 pm »
Quote from: Magpie on April 03, 2011, 05:17:53 pm
So it's sat for a few days and if I turn the bars hard right there's no drag, hard left it drags.
Cliff.
Cracked upper triple??
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Offline jvandyke

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Re: CB750-Front Brake Dragging.
« Reply #36 on: May 18, 2011, 07:06:25 am »
I'm working on reducing drag on mine too. I did discover that if the brake line is bent a bit it applies pressure to the caliper that effects the swing arm adjustment.  I couldn't get good adjustment until I tweaked the pipe so it wasn't trying to pull on the caliper.  I'm still toying with mine but suspect the piston seal might be dirty, small hole in res seemed to have been gunked but even once cleared, I still have drag.  Will revisit tonight.  Just wanted to point out the potential brake line factor.
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Offline tlbranth

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Re: CB750-Front Brake Dragging.
« Reply #37 on: May 18, 2011, 07:55:24 am »
The mechanical adjustment on the caliper has to be juuuuust so or it will drag.
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Offline jvandyke

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Re: CB750-Front Brake Dragging.
« Reply #38 on: May 18, 2011, 08:24:19 am »
I had the adjuster arm set for spec and free spinning wheel but applying brake induced drag.  Took caliper apart, looked good.  Checked return in master, clear.  Seems a bit better but it drags yet, not bad but not good either.  I assume it should almost free wheel with just a hint of rubbing if any.  I'm going to check that little hole again, bleed again and check adjuster again.  Apply brake and crack the bleeder to see if it squirts. Then I'll pull the caliper and remove the seal and make sure the groove is good, also checking for too much paint on pads.  If that doesn't do it I'll replace the seal I suppose.  This caliper was frozen when I got the bike and I cleaned everything up last year and rode it but it was likely dragging a bit all season.
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Offline tlbranth

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Re: CB750-Front Brake Dragging.
« Reply #39 on: May 18, 2011, 07:37:09 pm »
I know what you mean. Mine has some drag to it - all disc brakes do. I think the 750 is a little worse than most.
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1970 CB750 K0
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Offline seanbarney41

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Re: CB750-Front Brake Dragging.
« Reply #40 on: May 18, 2011, 09:08:38 pm »
The Honda pivoting caliper certainly has it's place in history...but not really the best design...
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Offline jvandyke

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Re: CB750-Front Brake Dragging.
« Reply #41 on: May 18, 2011, 09:09:45 pm »
Ended up pulling the seal, yep, gunk.  Scraped slot clean with allen wrench.  Got the proverbial whitish goo out.  Reassembled and now releases nice.  Barest hint of pad scrap but wheel spins "virtually" free.  Bit more work to do, haven't tried with wheel turned at various positions yet but MUCH better.  Thanks everyone, great site this, glad to have found it!  PS mine's a '72 500 not a 750 but same difference on caliper issues I imagine.
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Offline 76CB5WI

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Re: CB750-Front Brake Dragging.
« Reply #42 on: June 11, 2011, 08:13:20 am »
After reading this thread I thought Id ad my experience with my 750.
Original brake lines are not always good so if you have them...check them.
My top line was showing rust and occlusion and prevented the front brake
from releasing. I had a clean system top and bottom. I replaced the top line
and my problems were over..
Now this spring Im having the drag problem which could be result of all the
factors mentioned here but I think I will go ahead and replace my bottom line
just to be sure..so I can go ahead from there.
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Offline SohRon

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Re: CB750-Front Brake Dragging.
« Reply #43 on: June 11, 2011, 11:00:28 am »
Quote
The caps are DIRECTIONAL: they have a HI and LOW side to them. The gap side must be in front.

The gap goes to the rear:

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Offline Holshot

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Re: CB750-Front Brake Dragging.
« Reply #44 on: June 22, 2017, 07:25:37 pm »
Bookmarking for future... if a moderator were to perhaps read this, please think about implementing a "subscribe" option to threads. I'm a member to quite a few car/motorcycle forums and they all have that option which is nice when you want to recall a thread in the future but don't have a reason to reply and bump up an old thread.
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