Rear Brake Locking After Pressing Pedal

Hey everyone, this is my first post here. I've just picked up a '98 VFR800 and I'm really excited by it. The previous owner bought it in '99 and then it has sat for a long time (after he put 40k miles on it) because he had 3 other bikes he was riding. He's done a lot of work getting the bike back up and running and it's 90% of the way there at this point, but we're getting hung up on one main thing. The rear brake caliper is locking up when you press the brake pedal, but I think it is the center piston that's locking. From my understanding of the system, this actually shouldn't be possible.

One of the things we've done is rebuild most of the brake system. We've rebuilt all the calipers with new seals and cleaned up all the pistons. We put speed bleeders in all the calipers and the PCV. We bled the system (I've never encountered such a complicated bleeding process, holy cow) fully. After that, we found that the rear caliper was locking up when you press the brake pedal, but bleeding the center valve or the PCV frees it. Pressing the lever doesn't duplicate the problem (in fact, I test rode it around the neighborhood using only the front brake and it worked fine). It doesn't matter if the bike is moving either, pressing the rear pedal engages the rear brake and it doesn't fully disengage; subsequent presses get it stuck more and more.

I haven't pulled the caliper off to determine which piston is getting stuck, but considering the center valve and the PCV release it, it has to be the center piston.

I've ordered a replacement PCV to see if maybe that fixes things. Due to other threads I've found, I initially suspected the SMC but that doesn't make any sense to me since it doesn't matter if the bike is moving or not, unless it's possible the SMC is not behaving correctly and is just allowing the brake fluid to flow through but not releasing it.

Actually, that makes me think of another possibility: the guy I bought it from isn't as methodical in disassembling things as I am, so he didn't mark any of the brake lines. This left us with 4 brake lines for the front left; he says he connected them back properly by looking at the shape of the curves in the lines; if they're connected to the SMC backwards, could it cause this issue? EDIT: Nevermind, it was doing that before they removed any lines at all.

I was up until 1 AM this morning ordering the parts I need for the bike (tires, lights for the dash, etc), so I haven't had a chance to look at the bike in person, but I'm really excited to get it on the road (I've got a couple long trips coming up that I'd much rather take this bike on, with fully Givi luggage, than my Ninja 500) as soon as I can. Thanks for all your help!

A bad brake line can do that. I think it gets de-laminated inside and the fluid flows between the layers and expands the inner layer closed forming a check valve. Something to consider anyway.

Ugh, I'm hoping it's not that. How would one check for that?

My initial reaction is that I would think it's not that since opening a bleeder valve releases it, but maybe that doesn't really rule it out?

I've had a similar problem then I realized it was the pivot where pedal is turning over that was binding - a disassembly and lube fixed that - maybe not in your case but just a tip.

Helweg Denmark

I've had a similar problem then I realized it was the pivot where pedal is turning over that was binding - a disassembly and lube fixed that - maybe not in your case but just a tip.

So the pedal was essentially not returning to the fully disengaged position? I'll certainly check that, but I don't know that it would cause the center piston to engage without the bike moving.

Isn't the centre piston connected to the front brakes? Pressing the pedal should not make the centre piston move at all.

keef

Isn't the centre piston connected to the front brakes? Pressing the pedal should not make the centre piston move at all.

Yeah, that's kind of my point, haha. I'm pretty mechanically inclined, but this seems to be behaving in a way that doesn't make sense.

The center piston is connected to the SMC, which goes through the PCV, all of which is fed from the rear reservoir. When bleeding the PCV and then the rear center piston, you pump the brake pedal to do so. This means they are connected, but my understanding is that it's the pressure from the SMC that engages the rear center piston. However, the pedal seems to be definitely engaging the rear center piston.

Update: I've replaced the PCV, but to no avail. Bike still behaves exactly as before. I've ordered a rebuild kit for the SMC, but of course that won't arrive until next week. I've also ordered a full set of Galfer SS brake lines. If rebuilding the SMC and replacing the lines doesn't fix it, I'll be at a complete loss since everything else, except the front master cylinder, has been rebuilt or replaced at this point.

I'm not really concerned that the lines are a specific issue, but they're the original lines and the bike has 52k miles on it. The front lever feels a bit squishy and there's definitely no air in the system, so I might as well replace the lines while I'm at this. Getting new tires as well.

This is turning into a headache, but it's going to be great once it's done!

Check the rear brake & front slave master cylinder fluid return holes, if you get some swarf or corrosion in the M/C to brake line area, then this can block & stop pressure relief I had that on a Honda rear brake before. Just strip & clean the M/C & ensure the return bleed hole is clear.

The rear master cylinder has been rebuilt and I know for sure the return hole is clear. I'll look into the return hole for the SMC in the factory service manual and see how difficult it is to get to. If it's not too bad, I may look at it while I'm waiting for the rebuild kit to arrive.

Make sure the push pin from the front break leaver to the master cylinder is the right way around.

It fits both ways, but the wrong way doesn't let the front master cylinder piston fully return, this in turn creates a slight drag in the SMC which in turn activates the rear centre piston, which will not return by itself.

Check that the SMC is moving freely when rear brake is not releasing.

If it's tight it's because the front lever pin is the wrong way around.

If it's that simple, I'm going to be pissed. When the rear brake is locked up, I can't move the SMC at all. I figured that was just because the system was pressurized. It does move without issue once I bleed the pressure out. It also doesn't seem to do anything at all when I actuate it by hand.

The thing that makes me think that it may not be that, though, is that they were having this issue before the brake system came apart. It's possible, though, that the piston was sticking, a caliper rebuild kit fixed it, but then things were installed incorrectly which recreated the problem. Also, I can drive around all day using only the front brake and it doesn't cause this problem. These factors have me thinking that the SMC isn't functioning correctly.

Lastly, I'm still very new to this system. Where, precisely, is this push pin? Is it the one that the lever depresses into the master cylinder?

The push pin Oz is referring to is between the hand lever and the master cylinder piston.

Hmmm, that part was never touched that I'm aware of. How can I tell if it's backwards?

I keep looking at this and keep wondering. Are you sure you bled brakes correctly since you did a lot of work on components and opened system up? It is my understanding that there is an order to bleeding. Your symptoms are also exactly the same as I had on my 2002 few months ago after I let air get into system. My center piston on rear would stick like yours, I could let pressure off with PCV bleed, could drive and use front brake only etc.... This is guide I used and followed. I bled in same order as indicated in post. I know this is for newer model and I am unfamiliar with earlier models such as yours but think it may still apply. Not sure if you had seen this or if it might be of help.

http://www.vfrdiscussion.com/forum/index.php/topic/70842-bleedingfluid-replacement-on-linked-brakes-wabs-on-6th-generation-the-ultimate-guide/

From memory, the thin end of the pin fits into the master cylinder piston, and fat end to lever.

It might be something else, but I'm betting a beer against myself to this being the problem.

60 seconds to check.

GigemVFR

I keep looking at this and keep wondering. Are you sure you bled brakes correctly since you did a lot of work on components and opened system up? It is my understanding that there is an order to bleeding. Your symptoms are also exactly the same as I had on my 2002 few months ago after I let air get into system. My center piston on rear would stick like yours, I could let pressure off with PCV bleed, could drive and use front brake only etc.... This is guide I used and followed. I bled in same order as indicated in post. I know this is for newer model and I am unfamiliar with earlier models such as yours but think it may still apply. Not sure if you had seen this or if it might be of help.

http://www.vfrdiscussion.com/forum/index.php/topic/70842-bleedingfluid-replacement-on-linked-brakes-wabs-on-6th-generation-the-ultimate-guide/

I have seen that guide. I'm pretty sure it's bled properly, but I can make mistakes. The VFR800FI is basically the same, it's just "missing" one of the PCVs that the 6th gen has. Additionally, this problem was present before the system came apart, so I don't think it needs to do with bleeding.

VFROZ

From memory, the thin end of the pin fits into the master cylinder piston, and fat end to lever.

It might be something else, but I'm betting a beer against myself to this being the problem.

60 seconds to check.

I guess I'll hold you to that?

VFROZ

From memory, the thin end of the pin fits into the master cylinder piston, and fat end to lever.

It might be something else, but I'm betting a beer against myself to this being the problem.

60 seconds to check.

Just checked, it's definitely in correctly. I guess you owe yourself an unbeer?

OK, another update. I think I've narrowed the problem to the SMC, but I just rebuilt it and the problem hasn't gone away, though it has changed slightly. If I let it sit for 20+ minutes, the pressure dissipates by itself, which I don't think it did before.

Here's what I know:

• The caliper isn't sticking; if I actuate just the SMC, it works like it should
• The lines from the SMC to the caliper, as well as the PCV, are fine due to the above
• The return on the RMC is fine
• The center piston on the left side retracts fine even if the caliper is stuck, so there is no pressure in the incoming line from the RMC
• The pin in the front MC is in correctly
• All calipers have been rebuilt
• The PCV has been replaced
• The SMC has been rebuilt
• The RMC has been rebuilt

This tells me that it is almost certainly the return hole for the SMC, but I'm not sure how to clear it properly. There's a filter built into the port for the incoming line that makes it basically impossible to get to the hole. I tried blasting it with some compressed air and the air seems to flow fine. Any suggestions? Any corrections to my logic?

For the moment, I think I'm going to just block off the port coming out of the PCV and block off the port into the center piston on the rear and ride that way. There will be very little reduction in power and I can get riding this thing that way. My dad and I are taking an 800 mile trip in a week and a half and I'd like to have a few miles on the VFR down before we start (and I'd much prefer the VFR to my Ninja 500 for a trip like that).

I do have SS lines coming in that I will be trying to install, at which point I'll again have the whole system apart. If I have some suggestions to try with the SMC by then, I'll give them a whirl.

Having a beer as I type.

Make sure the spring behind the SMC piston is still there.

Yes, the spring is there. When I rebuilt it, I put in the new spring, in the correct orientation.

Another update: Well, I've sidestepped the issue. I took one of my old banjo bolts from my EX500 and had a friend plug weld it. I replaced the bolt with the modified one on the incoming banjo. This allows the fluid to continue to the center piston of the front but prevents it from entering the SMC. By relieving the pressure and retracting the center piston of the rear caliper all the way, I've effectively made that part of the system inert. This does leave the fluid in the system, so hopefully that means it won't corrode like it might if it were emptied.

This "fixes" the issue until I can figure out why the return on the SMC isn't functioning.

 Hi.  Just went through this problem and hope my solution is yours.

Symptoms.

On my 2000 VFR 800 I replaced all brake pads and bled the system and got a locked up rear wheel for my effort that was traced to the center brake piston not releasing.

While locked up, if you open the bleed nipple on center piston, fluid under pressure escapes and the wheel spins.

Going back through the brake circuit and pumping the brake to charge the hydraulics and testing each point for pressure release it led me to the SMC.

The Cause

The rear brake fluid reservoir supplies fluid the the rear brakes and the rear brake controlled front brakes, and everything else that's something to do with brakes other than 4 pistons of the front callipers. For some wonderful reason known to Honda they decided to insert another screen filter into a locked system and the process of bleeding all those metres of piping with fresh fluid puts all the years of crap into it and blocks it. Instant one way hydraulic lock-up. And I put it to everyone that if you clean it, and I'm comparing before and after my initial fluid change, the braking system comes back to how it was new.

The Solution.

Disconnect hoses and remove the calliper with the SMC.

Remove the 2   8 mm bolts on the cover

Remove the O ring.

Look at the green screen with all the crap in it.

Cleaning the screen from the outside is a waste of time. you actually have to remove it. Compressed air or mouth to mouth on the bottom hole of the SMC will pop out the green thing that actually turns out to be something much bigger and full of crap. 

Disclaimer, i'm sure it probably wasn't designed to be serviced so if you break it then try and find a new one or buy a whole SMC.

What you have to do is carefully get a fine flat blade screw driver and open the mesh cap, there are little tabs to work with. If you succeed, you will find a spring and ball, put them aside and now you can clean the screen. While you have the filter out make sure the 2 SMC holes are clear.

Put it all back together  and bleed the system, front, middle and rear points to a reasonable level and have fun spinning the back wheel by hand. You may notice that the wheel locks for up to 10 secs and frees. This is because you can't actually prime the SMC easily and there's a bit of an air lock going on and only riding does the correct action. You'll also hear a squishing sound from the SMC. No prob, the front brakes will save you while they pump the system and you do a few more bleed cycles.  obtw, the manual says to bleed the rear middle calliper, remove it. If your patient and don't mind a bit of fluid mess, an 8 mm ring spanner will fit while its on the bike.

End result and test

After the repair, I've noticed now is that on rear brake application at steady foot pressure, a moment later i hear the hiss from my sintered pads on the front disks followed by i think more stop on the rear. 3 sections working together.  

I won't be one that considers the system as rubbish. This is a mechanical system that after 16 years had a problem that could  be fixed with just a hell of a lot of patience and perseverance. I don't believe current electronically controlled ABS systems in 16 years would be so kind.  

You are on the right track, just get that filter out.

Cheers

Glen

Just a thought here but do you all ever look at the factory shop manual? It got all the routing info for cables and hoses. Also shows how to rebuild every component on the bike and is downloadable on this site. 

Most of the brake problems I've run in to are the result of not changing the brake fluid. I did find a de-laminated brake hose on 40 year old CB400/4 as well as a stuck caliper piston. Make sure the return orifice in the mastercylinder isn't plugged. You can use. .009 guitar string to clear it... carefully! 

I just had my front end apart on my second 98 VFR in order to service/rebuild the forks, clean the brake calipers and was thinking of finally installing new brake lines. I've never, ever had a problem with either bike, both 15 yrs. old. While cleaning the calipers I was surprise how clean the pistons were but also how much brake dust was in all the nooks and crannies. All six of the pistons easily pushed back into the calipers with only finger pressure. The oem pads had plenty of life left so they got reinstalled. I think you can do an easy job of cleaning the calipers up using either HondaBrite (actually S100) or aluminum wheel cleaner and a good stiff brush. 

By the way, the notchy feeling from the steering head bearings turned out to be the 15 year old hardened grease on the bearing races. Cleaned and retorqued (good idea to use the special socket from Honda for that- don't know how you'd ever get it correct without it), it feels like a new bike.

Also, installed Jamie Daugherty's damper kit. For the money, one of the best kits out there.

Mac Morgan

2016 at 10:16 AM, GleninAus, April 25

 For some wonderful reason known to Honda they decided to insert another screen filter into a locked system and the process of bleeding all those metres of piping with fresh fluid puts all the years of crap into it and blocks it. Instant one way hydraulic lock-up. And I put it to everyone that if you clean it, and I'm comparing before and after my initial fluid change, the braking system comes back to how it was new.

This, this right here. It's what I believe the issue is as well.

This will probably be a winter project, since I've worked around it and gotten the bike safe to ride, just without actually actuating the rear system from the front. I had a friend weld shut a banjo bolt I had lying around that's the same size as what the VFR uses. I put that in to prevent any brake fluid from entering the SMC, which did the trick. I'll pull it apart later and try to get that screen out.

10 hours ago, Mac Morgan

Just a thought here but do you all ever look at the factory shop manual? It got all the routing info for cables and hoses. Also shows how to rebuild every component on the bike and is downloadable on this site.

I have a FSM, both the physical one and the digital one from this site. GleninAus hit the nail on the head with his analysis. Everything, including the SMC, has been rebuilt. Many of the lines are still old, but I've confirmed they flow fluid in both directions and I have a full replacement set; just have only put on the front lines and the clutch line.

Can you link to that dampener? I'm assuming it's a steering dampener. I looked on the website and couldn't find anything.

24 minutes ago, iThinkergoiMac

This will probably be a winter project

One hours work, just do it, get some resolution and enjoy your summer :-)

7 hours ago, GleninAus

One hours work, just do it, get some resolution and enjoy your summer :-)

It's a little more than that since you have to bleed that caliper twice and either empty the braking system or let it drip. Besides, at this point, it performs flawlessly; it just doesn't activate the rear wheel when I hit the front lever. Considering it acts just like virtually all other bikes, I'd say I'm going to enjoy my summer, haha.

2016 at 7:16 AM, GleninAus, April 25

 The Solution.

Disconnect hoses and remove the calliper with the SMC.

Remove the 2   8 mm bolts on the cover

Remove the O ring.

Look at the green screen with all the crap in it.

Cleaning the screen from the outside is a waste of time. you actually have to remove it. Compressed air or mouth to mouth on the bottom hole of the SMC will pop out the green thing that actually turns out to be something much bigger and full of crap. 

Disclaimer, i'm sure it probably wasn't designed to be serviced so if you break it then try and find a new one or buy a whole SMC.

What you have to do is carefully get a fine flat blade screw driver and open the mesh cap, there are little tabs to work with. If you succeed, you will find a spring and ball, put them aside and now you can clean the screen. While you have the filter out make sure the 2 SMC holes are clear.

You're talking about the front left caliper with the Secondary Master Cylinder attached, right? I'm afraid I can't map what you're writing about to what I'm seeing in the manual (pp. 15-23). There, they describe a snap ring, push rod, master piston and spring. No description of an O ring, green screen, or spring and ball. Do you have any pictures, or can you help me map your description to what's in the manual?

I'm afraid I'm in the same camp: 2001 VFR, rear brake dragging, pumped the SMC about 50 times to push out the center piston on the rear caliper for cleaning and inspection (it looked fine), and now I can't push it back. Outside pistons returned fine with thumb pressure.

Found a picture of the factory rebuild kit; is the screen you refer to part of this?

[image: 45620mbg026-piston-set-second-master-cylinder-honda-xl-1000v-varadero-.jpg]

Could be like this

[image: 10i76vn.jpg]

12 hours ago, RogerRamjet

You're talking about the front left caliper with the Secondary Master Cylinder attached, right? I'm afraid I can't map what you're writing about to what I'm seeing in the manual (pp. 15-23). There, they describe a snap ring, push rod, master piston and spring. No description of an O ring, green screen, or spring and ball. Do you have any pictures, or can you help me map your description to what's in the manual?

I'm afraid I'm in the same camp: 2001 VFR, rear brake dragging, pumped the SMC about 50 times to push out the center piston on the rear caliper for cleaning and inspection (it looked fine), and now I can't push it back. Outside pistons returned fine with thumb pressure.

The manual has no reference to the procedure I've explained. As I said, "Disclaimer, i'm sure it probably wasn't designed to be serviced so if you break it then try and find a new one or buy a whole SMC".

First,follow the process of finding what part of the system remains under pressure, making the rear center piston not return.

If SMC is last stop, and remember the foot brake fluid reservoir feeds the SMC even though its meant to be activated as a front brake action but I think the one way valve that's clogged was where I found the problem. So you can partially bleed that system with the foot brake.  Its a complex work of  Honda engineering art but I think that if the foot brake pressure being applied is larger than the pressure being applied by the SMC then it overrides.

When you remove the hoses attached to the SMC you will see the plate held in by the 2*8mm bolts.

Sorry no pictures, I was trying not to go insane at the time trying to fix it.

I remember when I got the bike, I saw the brake system an remarked to my friends that I hope I never need to fix this. Looks light a nightmare .... yeah........ 2 weeks later.......ugh!!

But, now its fixed, really NICE big difference. 

12 hours ago, GleninAus

First,follow the process of finding what part of the system remains under pressure, making the rear center piston not return.

As far as I can tell, the possible culprits are: 1) the rear caliper; 2) the PCV; 3) the SMC; 4) the rear MC. How does one go about identifying the problem component?

I assume that it's not the rear caliper because the outer pistons retract fine. I'm guessing that clears the rear MC as well, at least it's return hole.

The SMC moves freely and pushes the center piston on the rear caliper out. However, it just can't be pushed back.

3 hours ago, RogerRamjet

As far as I can tell, the possible culprits are: 1) the rear caliper; 2) the PCV; 3) the SMC; 4) the rear MC. How does one go about identifying the problem component?

Pump the brake peddle to lock the rear brake and release,( unlike bleeding the brakes no pressure to be maintained to peddle as we are looking for a blockage) crack the bleed nipple, if it squirts and releases the wheel, move back along the circuit and repeat the priming procedure. Start from  ( your numbers) 1 goto 2 and on 3, identify the banjo bolt ( as there is no bleed nipple) on the brake line that runs to the SMC and crack that. That will be the final point of failure if you have a blocked screen or valve in the SMC.

Okay, back to the project. I'll describe as best I can the steps I think I need to go through. Please help me fill in the blanks.

Current state: Rear caliper off wheel, center piston extended and can't be pushed back (pictured). Pressing rear brake pedal extends two smaller pistons, which can easily be retracted with thumb pressure. Pumping Secondary Master Cylinder (SMC) on left fork leg extends center piston (took about 50 cycles to extend it as shown).

1. Open the center bleed nipple on the rear caliper (the one without the rubber boot in the picture). Fluid should squirt out due to pressure in system. Should be able to return the center piston with the nipple open. If not, rebuild the rear caliper.

2. Close the bleed nipple and add fluid to the rear master cylinder if needed.

3. Reinstall the pads & insert a block of wood between them or reinstall the caliper on the rotor (need to provide something for the piston to push against).

4. Pump the rear brake pedal and release. Pressure should be present against rotor/block of wood.

5. Open the bleed nipple on the PCV. If fluid squirts out, then <what?>, else <what?> 

I suppose that if the PCV bleeder is upstream of the actual valve and it squirts, that points to problems further upstream. On the other hand, if the PCV bleeder is downstream of the actual valve, it should squirt whether the PCV is the culprit or not, right? I'd really have to crack the inlet & outlet hoses to know for sure.

I just read Section 21 of the 5th gen manual, which goes into more detail of the LBS, but haven't quite decoded how to fully diagnose the issue. I do see how the PCV internals could cause this behavior if they're not working right, though.

[image: IMG_3194.jpg]

I've narrowed it down to the SMC; it can't possibly be anything else.

• The caliper has been rebuilt
• The PCV has been replaced
• The RMC has been rebuilt and the return hole ensured clear
• The SMC has been rebuilt

Another poster nailed it on the head a few posts back. It's almost certainly the screen in the SMC causing problems. Everything else apart from the lines themselves has been rebuilt or replaced.

4 minutes ago, iThinkergoiMac

I've narrowed it down to the SMC; it can't possibly be anything else.

• The caliper has been rebuilt
• The PCV has been replaced
• The RMC has been rebuilt and the return hole ensured clear
• The SMC has been rebuilt

Another poster nailed it on the head a few posts back. It's almost certainly the screen in the SMC causing problems. Everything else apart from the lines themselves has been rebuilt or replaced.

IThinkergoiMac, that's for your bike, right? I haven't rebuilt or replaced anything at this point on mine, and my components seem pretty clean and corrosion-free, at least from external inspection.

6 minutes ago, RogerRamjet

IThinkergoiMac, that's for your bike, right? I haven't rebuilt or replaced anything at this point on mine, and my components seem pretty clean and corrosion-free, at least from external inspection.

Right, sorry, misread your post.

With the way the system works, you can pretty quickly narrow down the problem.

• If loosening the bleeder on the caliper allows you to return the piston with thumb pressure, the caliper should be fine. If not, the piston is sticking in the caliper.
• If loosening the PCV allows you to return the piston, the line itself doesn't have a problem. The bleeder is after the PCV mechanism.
• If the outside pistons retract, the return to the RMC is clear.
• This leaves the SMC; if all the other steps clear, the SMC must be the problem.
• Either the SMC needs rebuilding or the screen is an issue like on mine.

8 minutes ago, iThinkergoiMac

If loosening the PCV allows you to return the piston, the line itself doesn't have a problem. The bleeder is after the PCV mechanism

Loosening the PCV bleeder, not the banjo bolts, right?

If the bleeder's downstream from the PCV, and loosening it allows me to return the piston, that doesn't eliminate the PCV as a possible cause, does it, because the PCV could still be holding pressure upstream? It seems that the PCV and SMC are still both possible culprits, and I can only know it's the PCV if cracking the banjo bolt at either end of the SMC-PCV hose doesn't allow me to return the piston. That would mean the PCV is holding line pressure even when the upstream pressure is removed.

It's a fascinating system, but troubleshooting's a pain, as you can certainly attest!

If you want to eliminate the PCV as a possibility, loosen the banjo bolt that goes from the SMC to the PCV and then depress the center piston on the rear caliper. If it flows, the PCV is not keeping it stuck, as you said.

It's complicated, but once you get a grip on it it's really not too bad, if a bit over-engineered.

Well, opened the center nipple on the rear caliper and the center piston still would not budge. Pumped the SMC and fluid flowed. Looks like the center piston has an issue, so I removed the caliper and plan to do a rebuild. The fluid is clear (no water, dirt, or corrosion) but I'm seeing what looks like little black bits of rubber. Time to order a caliper rebuild kit.

Just a major Oh Wow.. and just another reason these linked brakes are going By By.  thanks for a great read,  makes me know for a fact I'm doing the right thing.  Good luck guys. 

I'm reviving this thread to see what the resolution to this was. Anyone know? The beauty of the great interweb, problems get posted, solutions don't always make it into print.

I'm also thinking a de-link would be a great solution...

people insist on creating these DIY’s without photos and it drives me NUTS!

this is the “green screen” they are taking about. It’s under a banjo bolt in the secondary MC. 

I removed the brake calipers because they were covered in brake fluid and grime. I wanted to clean them. 

While they were out I replaced the seals with K&L seals (MISTAKE!!!!!!) and rebuilt the master with All Balls rebuild kits. The clutch MC worked fine, but the brake MC was not sized correctly. I cleaned out the green screen, but mine wasn’t dirty really. I thought putting it back a certain way mattered, but it actually doesn’t (it can be put back any one of 360*).  

I bled and bled and bled and couldn’t get it to work, so I sent it off to Honda for work and winter storage here in Ohio. 

My dealer replaced all 12 seals on the calipers, and rebuilt the brake master cylinder with OEM seals. Then they bled the shot out of it and the problem went away. It’s air in the secondary MC line. That’s what my dealer came to the conclusion of. I’m a happy camper and now I’ll probably get increased MPG’s! Wooooooo! Only cost me $269 for the dealer to diagnose, replace parts, and bleed new fluid!

[image: B809A55F-B863-4187-8A74-57CC395FB0D2.jpeg]

Nice write up Urban. Having the pics do help. I'm going to be faced with bleeding my whole system and have the front calipers on the workbench now waiting to be rebuilt. Now I know where the famous green screen is. 

Just giving this a 2018 bump as I've just come across the stuck center rear piston and have traced it back to the SMC.

Never knew about the green screen, so many thanks to GleninAus for his comprehensive troubleshoot. And Urbanengineer for what it is I'm looking for.

Here's hoping it fixes the problem... as it almost destroyed my rear disc and wore down new pads in under a year.

Looks like I'm gonna get my hands dirty again tomorrow morning.  :comp13:

Not sure what happened to my post... but

I read this article not long ago - https://www.sportrider.com/sportbike-for-sport-coat-crowd?con=TrueAnthem&dom=fb&lnk=TA&src=SOC&utm_campaign&utm_content&utm_medium&utm_source#page-9

"When the foot lever is actuated, the secondary master located on the front left caliper is back-pressurized so that the braking of the front wheel does not cause additional braking at the rear. In short, using the linked foot lever for braking delinks the other system."

Maybe this is what this valve is for... dunno, took some pictures while I had it apart, clean and the brakes work fine.

[image: valve1.jpg]

[image: valve2.jpg]

[image: valve3.jpg]

Vee-Ef-Ar, 2/26/2018 at 12:03 AM

Not sure what happened to my post... but

I read this article not long ago - https://www.sportrider.com/sportbike-for-sport-coat-crowd?con=TrueAnthem&dom=fb&lnk=TA&src=SOC&utm_campaign&utm_content&utm_medium&utm_source#page-9

"When the foot lever is actuated, the secondary master located on the front left caliper is back-pressurized so that the braking of the front wheel does not cause additional braking at the rear. In short, using the linked foot lever for braking delinks the other system."

Maybe this is what this valve is for... dunno, took some pictures while I had it apart, clean and the brakes work fine.

[image: valve1.jpg]

[image: valve2.jpg]

[image: valve3.jpg]

Good man! Thank you for coming back and bumping this. There isn't enough info on this guy.

I think it mainly comes down to the usual suspect problem of people not changing brake fluid on time. Oh bother, now both our bikes work :). 

Too bad I can't ride mine right now though, snow is falling! (pic added below to immortalize it on VFRD)

[image: SMC green thing.jpg]

I have a very similar problem. In the Honda Gen Workshop manual they list a probable cause as an incorrect Length of the secondary master cylinder pushrod.

The manual does not give you the correct length. Honda Australia seem unwilling to help, all my local deadlers have no idea. There fore does any one actually know what the length should be. I note the rear master cylinder lengths are in the manual.

I am very close to throwing the towel and de linking the Brakes.

Has any one just tossed the screen out or does the one way valve / check valve have a real function ?

For the life of me I can't see how the secondary master push rod length could have anything to do with it, or how they could be different from one bike to the other.

The check valve in the other hand, is needed.

Most linked brake problems are due to wear and/or bad history of cleaning.

There is too many places to clog up with sludge, and its hard to clean without complete dismantling.

Hello VFRoz, I can only presume that if the Pushrod length was set too long that it might block a return port.

I have now rebuilt both Front Calipers, secondary Master cyl, replaced PCv,Re built Front master cylinder, rebuilt rear caliper.

Cleaned the "Filter / one way valve" as mentioned earlier.

I was going to replace rear master cylinder as mine has a slight amount of wear, but have been told this item is now discontinued.

This is the second attempt at fixing properly, and we still have the centre rear piston locking onto the brake rotor.

We have blown all lines out and flushed nearly 2 Litres of brake fluid through.

It feels as if the only thing we have not done is check the installed length of the Secondary Master Cyl pushrod.

There are two mentions of the secondary master cylinder pushrod in the manual.

But no dimensions.

Is the secondary master cylinder pivot (bottom mount) free to move?

Or is the front left caliper dragging?

Is the secondary master spring ok?

Does the pushrod go in straight to the master?

I'm running out of ideas.

No sure which manual you are using, I could not find any reference to push rod length.

Sorry, I did find it.

I can measure my old one I pulled out when I delinked.

[image: IMG_3935.jpg]

It is flush with the bracket

Thanks VFROZ,

As a matter of interest / Frustration what did you do to delink the brakes?

I am getting so frustrated with what on every motorcycle is a simple hydraulic circuit.

I tend to agree with your earlier comments that most problems are caused by essentially years of neglect.

This doesn't however make it any easier to correct, esp now as more and more parts are being obsoleted.

pd1335, 3/20/2018 at 4:18 PM

Has any one just tossed the screen out or does the one way valve / check valve have a real function ?

As per my post in the article I read - "When the foot lever is actuated, the secondary master located on the front left caliper is back-pressurized so that the braking of the front wheel does not cause additional braking at the rear. In short, using the linked foot lever for braking delinks the other system."

My SMC pushrod length was the same as VFROZ's during my trouble shoot.

TBH I never knew it was adjustable and I doubt would be the cause of concern, unless some ungodly modification has been made.

Follow iThinkergoiMac's steps

With the way the system works, you can pretty quickly narrow down the problem.

• If loosening the bleeder on the caliper allows you to return the piston with thumb pressure, the caliper should be fine. If not, the piston is sticking in the caliper.
• If loosening the PCV allows you to return the piston, the line itself doesn't have a problem. The bleeder is after the PCV mechanism.
• If the outside pistons retract, the return to the RMC is clear.
• This leaves the SMC; if all the other steps clear, the SMC must be the problem.
• Either the SMC needs rebuilding or the screen is an issue like on mine.

I was able to bleed and retract the center piston at the PCV

Remove the green screen cover, remove and clean, then retract the center piston. You'll get a squirt of brake fluid from that hole (just to warn you)

Probably the two most important steps I took in my process was

1. Ensure that center piston is NOT sticking in the caliper, especially if there are no pads and disc and it's hanging all the way out there.

2. Bleed the system exactly how it tells you... ensure you remove and tilt the front left caliper (approx 15 degrees) and remove the rear caliper and have all bleeders facing upright.

I bled everything (bar the fronts) with the foot pedal. 

Delinking can be complicated or simple.

The path I followed was to replace the forks with VTR1000F parts, brakes from a CBR954 (front calipers) CBR600RR (master cylinder) and CBR600F4 (rear master). All of the above are bolt-ons that use the stock wheels and brake discs, and the rear brake hoses. You can just use VTR1000F fork lowers with VFR uppers and innards, the VTR parts have the correct mounts for Honda 4-piston brakes. VTR1000F brakes are not particulalrly good in my opinion. The only thing that needs fabrication is mounting the 5G mudguard, again not a big deal.Can't use a VTR mudguard as the fork leg spacing is narrower on those.

You could opt to keep the VFR front calipers and fork, but would need to source a suitably-sized master, and then connect all 6 pistons to that.The stock MC is a small diameter and I think would make for a grabby front brake, but you could try it and see; a 14mm master should be about right I think. 

The inner pistons in the front 3 piston calipers can be activated by drilling between the chambers within the caliper, or by using a bridging hose. At the back you can connect both standard brake hoses to the master using a double banjo, which will be freed up when you dismantle the LBS.