Hot rotor on rear brake

[Fire-medic]

Just replace that hose, don't mess-around with it. No, you do-not need to hold the pedal down. All you're doing by opening the bleeder nipple, is releasing the pressure from the collapsed hose, and allowing the pistons/pads to retract. Onward!

I've used earl's hoses, I think Summit carries them. They were much less expensive than the Spiegler or the Galfer hoses. You just need to know what the orientation of the end fittings are, to be sure of buying the correct one. Take pics of yours, and try looking online for something identical. You could use a protractor and a straightedge, or a sliding T-bevel, to learn the angles of the ends relative to the hose, and to each-other.

https://spieglerusa.com/

https://galferusa.com/

I just take my old hose to my friend who makes me stainless-steel covered hoses with new ends, identical to the OEM rubber ones. If the ends are in good shape, you could even cut-off the old hose, and use the ends to fabricate new hoses.

Have you tried PCW in your hometown?

PCW Racing
Address: 112 Henry St, Schenectady, NY 12304
Phone: (518) 346-7203

I checked, a new rear hose is <$44 from Ron Ayres, not-including shipping. The year doesn't matter as '85-'07 are all the same. That's not-even worth trying for a better price unless you have a friend who can fabricate them like my guy. Ron Ayres Yamaha is OEM, a dealer.

Hose, Brake
1FK-25874-03-00
$43.85

https://www.ronayers.com/oemparts/a/yam/500456adf8700209bc793156/rear-master-cylinder

 

[MaxMidnight]

This may answer some of your questions.

 

[Parminio]

Parminio, do I have to hold the brake pedal down when I open the bleeder valve? The brake does stop the wheel, it just will not back off enough and I get the pads dragging on the rotor.

No.

When it's locked up, just loosen the bleeder valve. If it's a clogged line / block then you should see a bit of fluid squirt out and the pads instantly loosen up.

What happens sometimes is you get a piece of garbage or an interior hose failure that acts like a one way door: when you hit the brakes the fluid forces the "flap" of deterioration open so the brakes compress, but when you take your foot off the brakes and the pressure tries to go the other way the "flap" of deterioration slams shut and wont let the fluid back off.

Hence your locked brake pads.

 

[HeckticHaze]

Ordered a rear brake hose. Talking end of the month before I receive it. Tried the test Parminio suggested. Brake drag still there after opening bleed valve(s). No brake fluid came out of the beeder valves.

I took off the caliper dust cover over the brake pads. I looked down at the two pistons. The inner one is out about 1/16" more than the outer piston. I thought the caliper would be more centered so the pistons extend evenly when the brake pedal is pressed. Went back to the Yamaha manual to see if I had any particular parts missing (washer) with the wheel mount or the caliper mount and everything is there. I will see what the new hose does.

Going to move on to the front brakes to keep moving forward with the repairs.

 

[Fire-medic]

The inner one is out about 1/16" more than the outer piston.

Not at-all uncommon, nothing to worry-about, unless one piston is frozen!

The 'no-flow' from the bleeder valve is a sign of an internal collapse, and obstruction preventing safe operation. Replacement of the brake hose and a good session of bleeding should solve that. Ensure that there is no crud remaining in the caliper before installing the brake hose, or you could end-up with another obstruction.

 

[one2dmax]

It sounds like you are on track. Taking and splitting the halves apart is no big deal and there isn't all that much you have to worry about for correlation when reassembling the halves. The bolts hold them very snugly in position for that (not a lot of slop in there to allow one side to cock in relation to the other side). Besides the caliper and master rebuild did you ensure that the master relief was also clear? It's the tiny hole in the master and if clogged will not relieve pressure properly.

Also,
The pads are not going to fully retract. They will come back JUST BARELY enough so that the wheel will rotate again with slight friction. You can just make out the movement when watching as you apply the brake and let off. Having the pistons off center slightly from each other in relationship to the rotor is also going to be a big deal.

 

[HeckticHaze]

I ordered an OEM rear brake hose from Ron Ayres. They got back to me a few days later and said the hose was back ordered until late September. I cancled the order. Did not want to loose 2 months of riding. I purchased a Spiegler hose. Just recieved it today. Kind of disappointed. I thought it would have the grommets like the OEM hose to fit in the bikes swingarm but it's just a plain hose. I'll have to wire tie the hose to the swingarm to keep it in place. Maybe tomorrow I can connect the new hose and bleed the system. Hopefully this works.

One2dmax I did clean that smaller pressure release hole in the MC. It was clean as a whistle when I put it back together.

I am still concerned that one caliper piston looks farther out than the other to make the brake pad contact the rotor. This is telling me an alignment issue. If that is the real issue, am not sure how I will fix that or what changed to make the alignment problem. I'll let you know how I make out.

 

[one2dmax]

The alignment doesn't need to be perfectly centered to function just fine without any problems. If it is grossly off center it would cause rubber on the rotor anyway.

 

[Fire-medic]

Having the pistons off center slightly from each other in relationship to the rotor is also going to be a big deal.

Sean, I don't know I understand this? I frequently have-seen one or the other of brake pads worn more-than the other, and also one piston in a different position in the bore, compared to the other, speaking of two opposed pistons. I can see where it would be a possible problem, where on a four-opposed pistons system (two pistons, each side) if two pistons on the same side were at different distances into/out-of the caliper block, there could be some-sort of 'cocking' of the brake pad.

Did you mean, Having the pistons off center slightly from each other in relationship to the rotor is also (NOT) going to be a big deal

 

[one2dmax]

I meant the inboard piston (or pistons) in relationship to the outboard piston (or pistons) is not going to matter if the caliper is off center some amount. An excessive amount would cause a potential for the piston to exceed travel when the brake pad is excessively worn and cause it to bind or cock in the bore when it loses stability from not enough in the hole.

If you have two pistons on the same side at different amounts sticking from the caliper touching the same backing plate then you have a problem. I do not believe this is what he is talking about.

 

[HeckticHaze]

Unfortunately the new brake cable did not work. Rotor is still getting really hot while driving. Before I put the new cable in i pulled the MC apart again an cleaned it. Made sure rubber internals were in the correct orientation. The only thing I have not replaced is the pistons in the calipers. They were just discolored not pitted.

Any other suggestions would be appreciated. I do not know what to look at next.

 

[one2dmax]

When you cleaned your brake calipers did you use new seals? If not that is likely your issue. They can swell even just a little bit over time causing them to not retract properly after letting off the lever.

 

[Fire-medic]

I agree with Sean, fresh seals will help the pistons to retract. Also another thing which helps the pistons to stay away from the rotor is the runout of the rotor. The runout helps to push-away the pistons from the rotor. Obviously on an in-spec rotor, there is not a lot of runout, but it's easy to understand how the 'high-point' of the rotor will push-back the pistons. Think of it like a comparison between a half dollar coin and a potato chip. Rotate either one on a central axis (spin them on-center) and it's easy to understand which one would be able to push-back the caliper pistons.

Since the pistons have heated-up the seals may have become cooked, and replacement should help to restore the retraction of your pistons. Don't forget, you have dust seals and piston o-rings, the square rubber pieces which fit into the machined grooves in the body of the caliper halves.

I like to use a Dremel tool and a brass bristle brush, shaped like a disc, to thoroughly-clean the grooves of the caliper. Then use brake fluid to lubricate the o-rings before you install them in the grooves.

As a matter of answering the question, please describe how-easy it is to move the pistons in the bore, before you charge the system with fluid. Can you easily use finger-pressure to move the pistons in and out? The pistons should move easily, they should not be sticking.

Also, please describe the appearance of the pistons in the bores. Does it look like a little bowl, or does it look like a solid, round bar (each piston)? Just trying to eliminate possibilities.

 

[HeckticHaze]

I did use a dremel and the brass wire brush as you described to clean the areas where the seals sit. They were completely clean. The pistons had some discoloration on them but no pitting. I did use some brake fluid in my cv leaning process. I used a compressor to blow everything out. I ran new brake fluid through the boxes, on the pistons, and coated the new seals before installing. I also used the red grease that came with the seals and coated the seals with it before inserting the pistons which seamed to slide in without much effort.

I was wondered about the runout on the rotor. I do not have a tool for that. Maybe Harbor Freight has them. If the rotor is warped, I would think you would feel it when you apply the brake. I am not getting any vibration. I see Yamaha discontinued the rear rotor. If it needs replacing has anyone used an EBC rotor?

I will pull the calipers again. I will see if I can remove the pistons by hand without the assistance of compressed air. How do you know if a piston is cooked? What are the visual indications? If the caliper body has been subjected to a high amount of heat for a considerable amount of time can it be damaged? I'll try and get some answers to your questions. Thanks for your input.

 

[Fire-medic]

If the rotor was warped, you could probably see it wobbling, watching it from behind the bike. You'd feel it in the pedal if it was that'bad. Ever have bad brakes on a car/truck, where you could feel the wobble while braking? If you don't have vibration on braking, that's likely not your issue.

There are plenty of aftermarket resources for the rotors. ebay motors of course. EBC and Galfer probably have 'em, but $$$. I'd try the ebay motors ones, seems like people here have used 'em with good results.

I've never seen a VMax caliper body go-bad. That doesn't mean it cannot happen.

What pads are you using? OEM or aftermarket? I once tried aftermarket pads, and I had a dragging brake after installing them, I'd pushed in the pistons and then installed the pads, but I noticed they were dragging enough to become too-hot to-touch after about a 10 mile ride. I disassembled things like you're doing, and like you're doing, I did it a couple of times, and checked the hose, master cyl & etc. I finally skimmed the pads a bit with a belt sander, and no-more issues.

 

[HeckticHaze]

I got the caliper off the bike but that is as far as I got today. I'll have to use the compressor to remove the pistons. Could not get a good grip on them to remove by hand. The PO had installed EBC pads. Did you just put the pad in a vise and take the belt sander to them? I may try that. I might grab some new pistons. The only thing I have not changed out.

 

[MaxMidnight]

I was wondered about the runout on the rotor. I do not have a tool for that. Maybe Harbor Freight has them. If the rotor is warped, I would think you would feel it when you apply the brake. I am not getting any vibration. I see Yamaha discontinued the rear rotor. If it needs replacing has anyone used an EBC rotor?

You don't need a special tool, a pointer fixed to (say) an axle stand close to the disc. Any significant run-out should be visible or alternatively measure the gap on four points around the disc with a feeler gauge.
You would not feel anything through the pedal unless the limit (0.15mm) is greatly exceeded.
The reason you do not feel pulsing is because as one piston is pushed in the opposite one comes out and thus no fluid is displaced (which would cause a pulsation).
This is also why a much smaller thickness variation will cause pulsing as both pistons will be pushed out which does displace fluid.

 

[HeckticHaze]

So I got the pistons out. Someone asked what the look like. There somewhat squared off. A cylinder with a cup inside. I do not think they look to bad. Some discoloration on the outer surface in spots. Cleaned the fluid out removed the seals and wiped them down.

I spoke to a friend that works for a local Yamaha dealer. He has 35+ years experience working on motorcycles. He said if you are using 3rd party brake pads do not use the shims that go on the back of the OEM pads. So I removed those. I also skimmed the brake pads with a belt sander as Fire-Medic had done.

So I am holding off buying new pistons. I think I will put the calipers back on the bike. Still thinking of pulling the innards back out of the MC and checking them and that weep hole.

 

[Fire-medic]

Disassembly of the master cyl is not hard with the proper, long-nose circlip remover, you need an internal circlip remover, one which makes the circlip smaller in diameter. I'd try using a tiny probe to clean that orifice, before tearing everything apart.

 

[HeckticHaze]

I'll pull the MC off again and take a look at that bypass hole. I have a special set of long nose circlip pliers I had to purchase for my 82 Seca MC. They worked well for the Vmax MC circlip.