sticky front break?

So, I've got a front brake that doesn't seem to want to retract fully. It comes back enough to let the wheel turn, but it's definitely still got some load on it. The pads seem to hold the disc more when the wheel's turned backwards too. The lever feels a bit squishy: it doesn't stop at a specific location when I pull it back - just continues to get harder to compress.

Is this just a classic "break bleeding" fix? I've never done it on this bike yet, but before I did I thought I'd see if I should expect it to help. If so, any words of wisdom or advice?

thanks,

 

This sounds like a case of brake fluid contamination--probably (and hopefully) just moisture. Before you start your brake bleeding procedure, drain, flush and refill your system with clean DOT 3 or DOT 4 brake fluid. If you see any black debris that looks like rubber from seals come out with the fluid, you'll need to inspect all components (hoses, master cylinder, and caliper) for damage.

 

Replacing old brake hoses to stainless steel is a performace upgrade. It is recomended after five years. I removed the elbow behind the headlight and ran one brake line from master cylinder to caliper. It firmed up the feel at the lever.

 

Any suggestions on how to flush the brake line? My Clymer makes no mention of it.

thanks,

 

I wrap the Bleed Nipple Threads with Teflon tape making sure the Bleed Hole is open.

Then, I attach a One-way Valved Bleeder into a Jar of Brake Fluid so NO Air is going back to the Caliper, what-so-ever.

As in the previous Posts ... I start the Bleed process by pumping-up the laever and holding it closed ... opening the Bleed Nipple to expel the air.

Once the Air is expelled, the Pumping will move the Brake Fluid through the system.
At that point ... I leave the Bleed Nipple OPEN and Pump Fluid through the Linds and Caliper until what is coming OUT is as clean as what is being replenished to the Master Cylinder all throughout the Bleeding process.

It takes a few minutes to expel the air ... the Bubbles travel down through the whole system and out the One-way Bleeder.
Once the air is out ... you're home free.
Each pull of the Brake Lever pushes fresh Fluid through the system and eventually out the submerged One-way.

I waste several ounces of Brake Fluid filling the Jar to keep the One-way submerged. But, is worth it for the nice, strong pressure that you develop when the process is done.

 

Murphy's law strikes again: I got the clear hose and new DOT 3 fluid, but when I went to pull the cover off of the master cylinder, one of the heads of the screws stripped! @%^#!! Oh, well there's worse things that can happen to a person.

Hopefully I can just drill it out and re-tap.

 

Easier than drilling - take your Dremel with a small cutting wheel, and simply cut a slot in the screw head. This should allow you to use a large slotted screwdriver to put more force on it. If that fails then you'll have to drill and retap. You may have to use up part of the wheel against a piece of scrap iron to get it small enough that you don't cut into the MC cover.

 

if it comes to drilling , use a bit that is slightly, just a wee bit larger than the threads on the one you got out
the hole in the cover is slightly larger than the screw
if you go slow and easy you should be able to drill the head off and take the cover off and get hold of the rest of the screw with some pliers

 

Okay, got the screw drilled and removed. Just need a replacement now 'natch. Used he same technique Polock describes. I'll have to remember the cut-a-slot approach. It might make me justify keeping my flat-head screw-drivers around. ;~)

However, after the flush and bleed the lever seems tighter (not so spongy), but it still doesn't feel like the pads are getting pulled away from the disc. It's sometimes hard to roll forwards and always sticks rolling backwards.

Maybe give it another try? I pumped 'till clear fluid came out with no bubbles, then closed the bleeder with the lever held in. I must be missing something.

 

HCP3040 master cylinder cover screw, each:
$ 1.00

- Make sure the caliper is properly torqued to the fork tubes.

- Make sure that the caliper pad Shim is in place correctly.

- Make sure that the Reatainer Plate-to-Caliper Pin and the bore in the retainer plate and in the caliper for that pin are in good shape, or otherwise the caliper is going to wiggle around and not remain "straight" on the rotor and that can cause some of the problems that you describe.

- Make sure the caliper piston is not siezed, or partially siezed, int he caliper bore.

- If all fails, use bigger hammers.

 

Oh hell, I forgot the most important thing!

On the "floor" of the master cylinder reservoir, there is a TINY hole that allows fluid pressure from the piston chamber to be bled-off when the piston is retracting. If this TINY hole is clogged, the piston in the master cylinder will not retract fully, or will be very sluggish in doing so. In turn, this will prevent the caliper piston from withdrawing completely.

This hole can become easily clogged, of course, due to its size. You have to use just one or two strands of electrical wire to poke through it and clean it.....did I mention how TINY it is?

 

okay, so I got the calipers apart, cleaned, and put back together and am still seeing the same thing. Some observations:

1) I "retracted" the piston after seeing if it would travel w/o pads or disc by using a clamp - not pretty, but it worked. ended pushing fluid back up into the MC (duh!) and out, so I suspect that the return path exists - but it still might be clogged

2) the pad against the piston had what looked to be a half a shim between it and the piston so I swapped the pads (left to right) to see if it would make a difference. nope.

3) last year, when I got my front tire replaced, i couldn't find the bushing that they use as a spacer on the axle so I fab'd one out of brass and put it on. it was about 2-3mm short and so I just sucked the axle nut down to compensate. I thought that there as a chance that this weird load could be causing a misalignment between the disc and pad. loosened the axle nut and still the same problem.

4) back to the return path - when i squeeze the lever "quickly" I can get fluid to launch out of the MC reserviour (with the diaphragm removed of course) like a fountain. Does that mean that the bleed-back path is clogged?

5) I did notice that when the pads do grab, i can see some relative motion between the calipers and the retainer plate when i move the wheel. there's a little rubber bootie, so i figured that they're suppose to move to some degree.

Is it time to bust into the master cylinder? why arent' these things ever easy? I suppose they wouldn't be as much fun then... :twisted:

 

Wow, I've never seen that, but of course I've never squeezed the lever with the cover off......just make sure the bleed-back hole is clear, that would be my recommendation.

You'd have to ask someone who has one of these bikes (I think 750 Seca models use the same caliper system as the 550's). I would think that the pin is the same size as the bore in the retainer plate and in the caliper, and that there shouldn't be much movement at all, but...........?

If it were easy, you wouldn't have the need nor opportunity to take everything apart and learn all the ins-and-outs of 25+ year old Japanese engineering design and production. Where else can you have so much fun with your clothes on?

Yes, you might want to clean that m/c relief port really well, and maybe even rebuild the m/c (neither expensive nor hard, just messy, but you're used to that by now!).

The older I get, the more important brakes seem to become to me.

 

Uh, #3 needs to be addressed. 3mm isn't much but it can cause alignment issues with the caliper. Get it replaced with the correct spacing.
Be sure to swap the pads back to their original positions as they have been bedded down to the pattern on the respective sides of the rotors.

 

I think I got it (good enough for the rest of the season anyway). I found that the boots on either side of the pin that connects the calipers and the retainer plate had been eaten away so badly that they were wedged between the pin and the bore. So as the disc pushed against the pads, the would just load up the boot pieces and bind. Therefore, any misalignment between the pads and disc would cause them to not be coplanar.

It's not perfect ( I was hoping to see it spin like it does w/o the calipers touching the disc - it just keep going, and going... ) and I still think that the master cylinder is not pulling the piston back far enough to allow the pads to get completely out of the way. but it's close enough for now - certainly better than it was. I'll need to replace those boots to keep crud from getting there and locking up the play (but wait that's what the original ones did); one more item for the winter repairs list.

BTW: Thx for the advice on the teflon tape. Between that and not pumping the brake fast enough, I think my previous attempts at bleeding where futile.

 

Slight contact with the rotor surface is normal for pads, I hope your not expecting them to rise off of the surface completely. I guess we could figure out a way to do that but I'm no engineer. I had the rubber boots on my calipers melt away from fork oil exposure so I have had issues with the pads hanging up on the pin. I still have not heard back from the nice folks at the rubber boot place. To date, stock boots are no longer made for my Seca but I hope they are available for yours! If they are, would you be kind enough to measure them out and post your findings? We might be able to adapt them for use on other applications.

 

sure thing. I'd be surprised if Chacal didn't chime in with a p/n and piece piece, but i suppose he can't carry everything.

I was thinking about it later and I bet if I used some high-strength double-stick tape (don't laugh, we use it to hold down parts that don't fit in a vice that need to be machined) I could secure one pad to the caliper housing and the other to the piston. The play in the assembly would then definitely need to be taken up by the pin connecting the caliper housing to retainer plate. But if it worked, then as the piston retracts it would pull the pad away with it; rather than relying on the disc to push it away. I'd probably remove the spring too (see below).

I'll let you know if I try it ... and it works ... otherwise, I'll just keep quiet.

 

I'd be leery of removing parts from a caliper. However, I note that the spring in question is to keep the pads from making noise so for the sake of trouble shooting, I suppose it would be alright, JUST THIS ONCE.

 

my 550 has draggin pads too. They all do drag a bit, but you shouldn't have resistance when you try to move the bike.

 

I used to have a ton of resistance when I moved the bike backwards (especially when the wheel was turned), but now I only really notice it when I've got the bike on a stand and watch the tire spin (or not as is the case).

These bike have great front bearings, it seems like a shame to waste it all by having pads that drag.

 

That the fluid "Fountains" up so HIGH in the Master Cylinder is a sign that the Pressure isn't being fully supplied to the system.

A little bit of expansion flow is Normal. But, an "Old Faithful" display is a sure sign that the Pressure Seal is leaking-by and the Volume in the Cylinder isn't going toward the Caliper.

It's leaking by that seal and the Pressure in the system is causing it too discharge from the tiny port intended to keep Fluid in the Master Cylinder chamber due to Brake Pad wear.

 

So is that a seal within the master-cylinder or within the break caliper? Would that lead to the break not retracting properly?

 

Master cylinder. Get yourself a new rebuild kit (OEM) and rebuild the beastie.

 

Need I say more?

HCP1694 Aftermarket front Master Cylinder Rebuild Kit, for all XJ550 models.
$ 32.00 plus shipping.

In stock, of course.......

 

When the system is Fully Bled ... it really does NOT retract all that very much.
Rather, the pressure is relieved and the Pads just don't make hard contact.

That's why you should CHAMFER the Leading Edges of the Pads. So they don't squeal ... and why you feel it inn the Brake Lever when the Rotors are warped.

 

so where's the quotes for the boots chacal? :wink:

i think my MC's working good enough for now. i'll put the replacement on my winter todo list. i think i'd rather spend some time and $$ on the fuel system next... Any suggestions for must-do's? like replace the fuse-box for the electrical side of things? I'm already planning on the new fuel-filter.

 

Yes, by all means replace that 1930's style fusebox! I sell the nice 6-circuit covered fusebox in my ad, and optional bottom gasket and fusebox circuit decal.

Check your alternator brushes, too, make sure they are the proper length.
Clean the communtator with some very fine (1000) sandpaper. Make sure every single electrical connection is clean and seal them with di-electric grease and/or the backs of the terminals with caulk.

Fuel system depends on what problems/issues you are having.....make sure your fuel filter (in-tank and an additional in-line filter) are up to snuff. I've got the fuel lines, scissor clips, filters, petcock rebuild parts (even complete petcocks), carb rebuild parts, etc.

Make sure the inside of your tank is fairly rust free, otherwise electrolytically clean it and whatever you do, don't coat the inside of the tank!

BOOTS: a no-go. Robert has a line on a company that might be able to make some! That would be great.

 

Fuse Panel

Clean electrical contacts.

Oil everything that needs it and some stuff that don't.

Get a small paint brush and give everything rubber a nice little Armoral Painting. Brake Lines and Bushings holding the lines.

 

What Boots are we talking about?

 

They press into the housing that holds the caliper (or maybe it's the piece that bolts to the fork?) and cover the brass pin with the funky clip that connects the two.