Another 5th gen rear brake problems

OOTV
Well... i remember that all times brakes were'nt dragging - bleeding was done with something between pads. But didn't noticed that in mind.
And all times i did that without anything = dragging.
Maybe my Linked system or LPCV has some glitch, which is unfound yet, but bleeding with unsticked pads help to avoid it.
It is surely somehow related to excess pressure in brake line. Or maybe just Brake pads retaining pin - but how?

TNRabbit
Sorry, not yet I did clean RMC with air (pressured on car wash station). Did clean with brake fluid and softy. I will check it tomorrow, no time today(

FJ12rydertoo
Yes, i'm sure that reservoir is not overfilled. Did install rear caliper first, then filled reservoir a bit, smacked rear pedal, SMC and front lever to get all pistons in place and then closed reservoir.
Btw, missed similiar thing in my story: Then i went to motocycle service at start of season, my brakes were soft and dragging a bit - it was hard to move bike by feet while sitting on it. They opened rear reservoir, then we desided to move bike to wash it before brakes bleeding - and dragging problem was solved!
I have tryed this solution this saturday and sunday - didn't helped.
Crazy puzzle

Please post something else i could check tomorrow. It's 8pm, i'll ride home today. Will start checking and acting like shaman tomorrow at 8pm, so, in 24 hours.
Thanks for your replies!

 

OOTV
I have tryed to lower pressure in system, in case if there is such, past saturday. Opened rear reservoir, pressed pedal few times. Then released some brake fluid from center valve on right front caliper and from valve under seat (one pedal press for each). Of course i closed valves before releasing pedal.
So this was kinda "releasing pressure" and "button up" bleed procedure for me.
Doesn't this procedure cross all our clues about this problem?
Brakes did get hot after that without using rear brake (but front was used a bit, as well as SMC).

Thanks a lot for the link!!! Will test PCV this way tomorrow too. Big thanks!

 

Sorry for late reply, did some stuff from TODOList yesterday evening. Results are sad :\
- Will check free wheels spin with jack-screw
= 3\4 turn with hard spin for rear wheel. 2\4 turn for front :O

- PCV check
= Unbolted the metal brake line at the PCV and pressed on the center piston of the rear caliper. Brake fluid comes out from PVC. So my PCV is fine right?

- Will check pistons moving with rear\front brake - do they return when i release brake
= Rear brake: 2 pistons from pedal rear brake move good, i can clearly see that. Center piston moves really for a bit by pressing SMC manually. I think this is bad.

- Will check Brake pads retaining pin
= WOW! Didn't even knew that brake pads should be placed in calipers that way! Usially, i just pressed them in like "cmooon gogo *smashes them into with foot*". Well, i saw that this pin was placed wrongly at rear caliper - as conceived, but a bit shifted on one side. So it could press one side of pad (the one which not move in caliper) to rotor.
I have cleared all pins on all calipers, placed all pads in correct way to be sure.
Damn, i was almost sure that problem was in this pin!

- Diassebmle RMC and clean it
- Screw hose from reservoir to RMC correctly
= Didn't had necessary tool to unscrew RMC, plus it was 00 AM and me alone with bike on the street under my house... I have skipped this part for now.

- Full bleed again with something between pads
= Done. Full bleed with good (again...) motorcycle brake fluid. With bid wrench between pads on front left and rear caliper. Some air came out (seems that after PCV check system catched some).

= Plus, did front bleed too. Lowered brake fluid level in both reservoirs to avoid problems with that.
Pressed brake lever\pedal\SMC to pump brakes. Did let them rest a bit, then closed all reservoirs and bike was done.

And finally, another free wheel spin for rear wheel. And again 3\4 of turn.
Then i shaked rear caliper a bit, so it move against rotor. Some freedom for pads. Vuala! 1 full turn on rear wheel.

Well, who cares about wheel spin. Test drive. 5 miles. Both brakes used a lot. Rear rotor HOT as hell! Front rotors - slightly warm.

 

Another notice.
Rear pad, the one which not moves (and holds with pin). Grinded on one side more then on another. The right side (if look on caliper installed on bike). I thinked that is because of retaining pin, if pad wasn't installed correctly. Or this is 1 from 2 of pistons, which are activated by RMC. But, they did move good. Really, left one did, can't be sure about right one - hard to see it with pads and wrench between.

In result:
PCV seems to be fine, SMC was rebuild and fine too i think. Maybe i need to check small holes in SMC? (did clean them last autumn). Or just do check - does SMC get pushed back if i press on center piston on rear brake?
RMC not rebuilt. But it works fine, if look on left piston (rear brake). Not sure about right piston.
And last theory - center\right pistons are bad and need replace, because they get stuck in some position.
All 9 pistons were in almost good condition. They all had some craters on them. Will post some photos from past.

 

Pistons, as they were last autumn after full rebuild.
First photo - front caliper pistons i presume. Really good.
Photos 2-4 - i think this one is from rear. Maybe center piston, dunno. You can see crater from different POV. Is such damage critical ?

 

Sorry for the delayed response but it looks like you've done just about everything there is to do! However, to answer the last question there, Yes it is critical. On my 5 Gen (2001) when I bought it had very little rear brake function, so much so that you could step on the rear pedal and still turn the wheel. Turned out 2 of the 3 pistons (outer ones) were nicked and the burrs of the nicks were rubbing the rubber seal and creating a very sticky film of rubber on the piston causing the pistons to barely move. The pistons were so jammed in there, that it took quite a bit of air pressure to free the piston. I essentially had taken the caliper off the bike and used an air compressor to pump air into the caliper banjo bolt hole, while I plugged the other banjo bolt hole in order to free the outer pistons.

I would have guessed that the slide pin was the issue based on your report and it sounds like the PCV is OK as well. One thing I do know is that when pressing the rear pedal, the SMC at the front left caliper does "reset" i.e. Expand. I have to assume this is due to the rear pedal pushing fluid through it. I do not recall though, if the SMC resets if you push in the center piston. I do know that if the pistons are expanding outward at a different rate, this could definitely cause the pads to bind, so if they are not moving close to equal, then it could be an issue inside the caliper itself. My recollection is that there are three holes inside the unit, where one hole leads to the center piston well via its banjo bolt hole and the other two piston wells share a channel and have their own hole to each piston well. Other than that I am at a loss as to what is going on. All of the things you have tried would have been where I would have gone through as well. Although if you still have not looked into the RMC, then all other things being checked and double check, it would point to the RMC as the issue IMO. Or the rear caliper piston well holes being blocked.

 

+1.........

 

OOTV
You are fully correct about mechanics of combined brake system and arragement of rear caliper i think.
But if SMC is working, pressing pedal should kinda reset center piston, i think that's correct.
If center piston is OK too. But i'm not sure if it is!

All holes between wells in rear caliper are ok too. Wells - special inside coating has erased a bit, plus some small scratches, but nothing critical i think. In this case more important are rubbers and pistons which slide into them.

All of my pistons aren't moving at same rate (both front and rear calipers). You should hold one with finger, to let second catch him up. Well, all pistons have different wear. So they aren't stuck, but some pistons are better then other. Really critical?

Another thing, that visited my mind minute ago is... If PCV is working well, or even if it doesn't! The pressure caused by brake fluid to center piston should go away by 2 ways - to SMC, then to RMC, then to rear reservoir. Or to neighbor rear brake wells and then directly to RMC and rear reservoir.
So, fauly PCV cannot cause such problem at all.
Am i right?
Even faulty SMC cannot do this.
Just imagine!

So... the only thing left is RMC, or bad Center\Side piston.
I have found used Rear caliper from breakdown in Honda service, 2001 year (mine is 99). Only for 29$ :O
Will take a look at him this evening, will buy if pistons are in good condition.
Will be better to replace Caliper, or take off pistons and replace them?

 

I'd start with inspecting the center piston and if it looks OK, then definitely get to the RMC. Not sure how easy or difficult it is to get parts in Russia, but there are plenty of places to order from here in the states, but the place I ordered from the pistons were on back order for about a month! To their defense, they were back ordered from Honda. Of course being somewhat impatient about it, I ended up picking up a 6 Gen caliper expecting to use that, when the pistons finally came in!

I usually prefer to grab new when I can and when it is cost effective. If the cost of the whole caliper is less than the new parts themselves and the parts are in good shape, I'd probably take the used part. Although the used part I bought was more than the sum of the parts, if memory serves me correctly, I was able to resell the 6 Gen caliper I bought so no money lost there.

 

Another sad result. Sorry for late post, im' kinda disappointed and lost.
"New" used rear caliper is in great condition, pistons are as well. Replaced.
RMC taken off, cleaned, everything is ok.
Full brakes bleed.
Using RMC pedal - all 3 pistons are moving back and forward as they should. (didn't check movement by SMC).
Another ride, feels great, nothing pulls the tail. But - rear rotor is really hot again.

Last 2 theories.
Bended rear disk - it has used conditoin now, maybe even thinner than it should be by manual. And maybe - bended. If it is - it could heat itself with pads.
Second - bended front left rotor. It pulls caliper and activates SMC. But - front rotor is not hot. Can it stay cold but pull SMC? I think SMC needs some good pull, and if caliper gives it, front rotor should be hot as well.
One of my front rotors is a bit bended actually, but i can't remember left or right. Also, i don't feel any pulsation in lever so it's not critical.
But i will try to switch left and right disk.

 

Sounds like the rear caliper is better if the pistons are moving more equally now. Definitely check the run out of the rotors. A bent rotor, front or rear isn't a good thing regardless of linked btakes.

Thanks for the update. Good luck!

 

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