Front brake sticking. Arg.

[whyzee79]

Hello,  I changed out my tires and when I put the front back on the wheel is now locked up tight.  I checked the little hole in the master and it appears normal and clear.  Any advise?  Probably need to remove calipers and replace seals?  Also, this is on a 87FJ1200 with a R1 blue dot conversion.  I have read on here that it is hard to bleed the fronts with the anti-dive set up which is still on there and seems to actually work a little too.  Any hints on this?  Thinking on replacing the lines with the RPM stainless lines at this time too.  Riding season is slipping away in my area and the bike sits on a stand.  Any help is appreciated.

[Pat Conlon]

The relief port in the m/c is plugged. Take the splash plate out of the bottom of the reservoir and clean out the bottom. When you squeeze the lever and release, you should see a small fountain of fluid return to the reservoir...Be careful with brake fluid, lot's of towels and a squirt bottle of water is a good idea to keep handy.
Still no worky? Then more cleaning is needed, disassemble the piston in the m/c and clean everything.
Might as well put new seals on the m/c piston while you have it out.
http://rpmracingca.com/proddetail.asp?prod=M%2FC%3AFRTBRKRBKIT
If you don't already have one, order the extended reach snap ring pliers, trust me, you need these:
http://rpmracingca.com/proddetail.asp?prod=MasterCylinderSnap-RingPliers

So...what causes this relief port to get plugged? Gunk hiding below the splash plate along with
Old oem rubber brake lines which crumble internally causing problems like this.
http://xjbikes.com/forums/threads/why-you-need-to-replace-original-brake-lines-w-pics.41400/

Replace your oem rubber lines, they are long over due.

Hope this helps

Pat

[X-Ray]

Pat is probably right on the money. This is what happened to me a few months back, drove me nuts, rebuilt the calipers etc, and still locked on. There are actually 2 holes in the bottom of the master cylinder, my little pin hole relief port was hidden under a fine layer of sludge, cleared that and all good again.

Oohh found it. Here's what hapenned to  me with some pics http://www.fjowners.com/index.php?topic=16291.0

[red]

I have read on here that it is hard to bleed the fronts with the anti-dive set up which is still on there and seems to actually work a little too.

Whyzee,

You can bypass the anti-dive units with nothing more than wrenches.  Remove the short brake line from the caliper to the A-D unit by removing the banjo bolts.  Use the short (one-line) banjo bolt to attach one brake line to each caliper.  Done deal.  If you want to remove the A-D units entirely, you would need block-off plates to replace them, and these plates must have oil passages for the fork oil.  The block-off plates are about US$100.00 (if you can find them) so I just ignore the disconnected A-D units in place.  I would doubt they work at all now anyway, and they were always more trouble than they are worth.  All IMHO, of course.  This little extra job will not help your present problem, but it may eliminate a few headaches later. 

I'd also recommend a new banjo bolt for the Master Cylinder-brake line connection, but get the one with a brake bleeder installed.  That gadget makes bleeding the front brakes much easier.  The same banjo-bolt-with-bleeder is a good idea for the clutch Master Cylinder, also.

[Pat Conlon]

Re: Anti dive block off plates, a visit to our Suspension Files section will suprise you.

[fjbiker84]

I experienced almost the exact same thing several years ago.  After replacing the front wheel (while installing new tires, wheel bearings, front brake rotors and pads) I noticed that the front wheel was stiff when I tried to spin it while on the center stand and the front raised in the air. At first I thought there was a problem with the new wheel bearings but later figured out that the problem was with the calipers not fully releasing.  After taking the calipers off I found out that the caliper walls were corroded behind the pistons preventing them from being pushed back far enough to fully clear the new rotors and pads. 

[red]

Re: Anti dive block off plates, a visit to our Suspension Files section will suprise you.

Pat,

Okay, a pair of A-D block-off plates do not cost US$100.00, they only cost
US$99.00 so, my bad.  Add a few more bucks for shipping, too.
       

[whyzee79]

Ok,  I'll order new hoses and a master caliper rebuild kit.  I'll take it apart today and see what's under the little shield in the master.  Probably should just order the o rings for the calipers too. I just find it strange that they worked fine until I removed the wheel.  I didn't open any brake lines just removed the left side caliper.  The right side stayed on the bike.  Now it also feels like there is air in the system. 

[Pat Conlon]

Whyzee, I would wait on the caliper seals. Definitely get new hoses and clean out the system and see how that goes.... lots of shit hides under that splash plate.

Red, you were right on for the price I just wanted you to know that the block off plates were not scarce, but readily available.

[red]

Hello,  I changed out my tires and when I put the front back on the wheel is now locked up tight.  Riding season is slipping away in my area and the bike sits on a stand.  Any help is appreciated.

whyzee,

Looking back on your first post, I can not believe that you got the wheel back on (and the disk back into the caliper), and there is now any problem with the hydraulics.  I can easily believe that the caliper should shift left and right, to center itself on the disk, and for some reason, it now does not do that.  Try loosening the caliper mounting bolts, before you tear into anything else, and get the caliper shifting loosely on the bolts first.  See if the brakes work normally then (do not ride the bike like that, this is a shop-only check).  If that "fixes" the problem, forget the hydraulics and clean everything mechanical that mounts the caliper to the fork, inside and out, first.  You may be missing a spacer at the axle, or a spacer may be installed at the wrong location.  I do not know the "Blue Dot" units, but that would be my $.02 worth.  Once you get everything sorted, torque everything to specs.

It's always a good idea to take digital pictures as you loosen and disassemble things, especially on "modification" assemblies, because they will not be detailed in any book.

[whyzee79]

Update.  I took off the little plate in the master.  There is no crud under it (it looks spotless) and I took a small nylon poker and checked the little return hole.  It spouts out fluid like you guys said it should.  I removed the caliper that I originally took off and checked the operation of it.  It seems two of the four pistons are not moving at all.  I also took the other caliper off and all the pistons move nice and I cleaned them up when they were extended.  I can probably get the stuck ones to extend.  At this point if I can get them to move can I just clean them good and go about my day or is this a seal problem.  I am definitely getting the lines after reading the info provided.  About the anti dive.  I understand taking the short hose off and using the short bolt but what about the fitting where the hose is bolted on the anti dive.  I would think a copper washer and block off bolt are needed there too? 

[red]

Update.  I removed the caliper that I originally took off and checked the operation of it.  It seems two of the four pistons are not moving at all.  I also took the other caliper off and all the pistons move nice and I cleaned them up when they were extended.  I can probably get the stuck ones to extend.  At this point if I can get them to move can I just clean them good and go about my day or is this a seal problem.  I am definitely getting the lines after reading the info provided.  About the anti dive.  I understand taking the short hose off and using the short bolt but what about the fitting where the hose is bolted on the anti dive.  I would think a copper washer and block off bolt are needed there too?

whyzee,

If you can get the caliper pistons moving, extend them a bit and clean the sides of the pistons with a green scrubber pad.  If they are rusted and pitted, you will need a caliper rebuild.  The only thing that retracts the brake pads from the disk after you brake is the flex of the rubber seals.  If they have gone hard (not likely if the other seals are good), then you will need a caliper rebuild.

If you remove the short brake line from the A-D units, that will be fine.  You can fill the hole with any short loose-fitting bolt, and seal it in place with some RTV sealant, if you wish.  The fork oil will not come out of the hole, either way.  Brake fluid should push a tiny piston to "harden" the front suspension, to prevent front-end dive when braking.  The fit of that piston is far too tight to allow fork oil to leak - it must prevent hydraulic fluid under very high pressure from getting into the fork oil, when working as intended.  I guess some rainwater could get into the open hole, but that would not affect anything in this lifetime.

[whyzee79]

Ok Red, thanks for the advise on the anti dive and the pistons.   Ill post an update when I get a chance to clean them out. 

[Flynt]

I guess some rainwater could get into the open hole, but that would not affect anything in this lifetime.

You can also flip the AD unit over on the fork...  still provides the bypass feature and puts the adjuster knob on top so it looks like something functional.  Also prevents the rainwater issue if there is one.

Frank

[whyzee79]

I think I will construct my own block off plates.  Thanks for all the help from everyone involved.  I have not had the time to fix this as of yet but at least have a plan of attack.