Front Brakes not Releasing on '13 1200

I left my house this morning and within a few hundred yards my front brake was attempting to lock on it's own. I was able to get it to release enough to return home, using rear brakes only. The bike came off the showroom about 10 months ago, and has about 8K miles on it. I ride it regularly. Anyone else seen or heard of an issue like this?

 

Some report grime causing binding, although for this I would think it would have been the worst when you first left the house. Unless it was binding when you left but you did not notice it?

http://www.bikersoracle.com/vfr/forum/showthread.php?t=116830

 

Thanks. I'll check for grime but my last ride was at highway speeds on a clear and sunny day, so they should be really clean. The lever also has lost it's travel... I update after I take it apart.

 

I don't know the 1200 but that sounds like a classic case of fluid not flowing through the return port back to the master cylinder reservoir. That usually coincides with old fluid & gunk blocking the return port. If cleaning that does not help, perhaps you will find a failed seal or some sort of cylinder binding.

Good luck!

 

Yeah, but it's a 10 month old bike with clear fluid in it that is ridden almost daily. I suppose there could have been some junk from the factory that found it's way into the return port. Really odd, but I'll check it out. Thanks.

 

be sure you don't fill the mc all the way to the top as there needs to be some air space above the fluid.

 

A binding calliper seal might cause drag but I don't think it would prevent the pads releasing, so I would vote for a blockage in the return circuit in the master cylinder as the likely culprit. If the 12 is the same as other M/Cs that I have looked at, you should be able to pick the small silver cover out of the fluid port at the bottom of the reservoir and see the intake and return ports. These should both be free flowing (don't be surprised when a little fluid squirts back from the intake as you compress the piston, its supposed to do that). You may need to disassemble the MC and clean out the ports if they are blocked. At the very least I'd suggest you bleed the brakes and run some fresh fluid through them.

 

Note I was referring to seals in the MC. I figured if the fluid was perfectly clean, maybe a seal prematurely collapsed or such. Am I using the correct terminology for today's master cylinder?

 

I removed calipers this morning and all pistons are moving freely and seemingly equally, so. Some additional riding verified that the brakes are releasing, but very slowly. I also verified that it only occurs when applying the front brakes, so it's not pads/pistons that are linked, for sure. The best theory seems to be a partially blocked fluid return into the master cylinder... I guess I am having a hard time swallowing that idea since the bike is nearly new, but the port is small so it wouldn't take much to block it up. The fluid looks like it just came from the bottle.

 

take your hand off the brake lever

 

So, even though the fluid was crystal clear and less than one year old, I decided to connect a power bleeder and replace the fluid. Initially, I could not get any fund to flow from the master cylinder into the calipers and into the power bleeder. It made some sense as the issue seemed to be related to fluid flowing to and from the master cylinder. I also noticed that the brake level had gotten extremely hard (rock hard) to pull while I was running the power bleeder. I gave the lever a hard squeeze and "pop" the lever moved and fluid started flowing. I finished needing the brakes and now it all works perfectly. At this point, I am not sure if I freed some small spec of debris, or a check valve, but not it's all working properly. A little odd, but, minimally I have fresh(er) fluid in the system now. I guess the moral of the story is "if you are having braking issues, bleed them even the fluid looks like brand new".

 

I would say from your description of the "pop" that it freed the return port blockage, Problem is which way did the bit of gunk go, did it go into the master cylinder or did it go back down the line which means it could work its way back up to the tiny return hole. 50/50 call but ride it and keep an eye on it

 

Agreed. Since it popped while squeezing, I am hoping it went towards and through the calipers. Time will tell!

 

motorn was having this issue last spring on his 2010 VFR1200 when we went for a ride ... bleeding the brakes helped temporarily.

I'm not sure what the actual solution was in the end. Maybe he can chime in?

 

Thank you. I'll definitely keep an eye on it, but I can say it's not just better, it's right now. It felt like the flies was restricted both to and from the calipers. It seems it would have to be either a blockage in the master cylinder or a valve issue in the abs module. I ran a whole bottle of fresh brake fluid through it, so we will see. If it does reoccur, I'll probably replace the master cylinder but would love to hear from anyone that had the same issue.

 

Before spending big bucks replacing entire master cylinder, take it apart and inspect plunger with rubber seals. I rebuilt my 83 MC with a new kit for $35 or so.

 

I hear you. Hopefully it won't reoccur.

 

I bought a used MC off eBay, and when I received it, it was seized solid. Luckily I was able to access the back side of the piston through the hose port, and push it out. The inside had crystal deposits that had been jamming the piston. These cleaned off easily and the part works great. It would not surprise me if you had something a little similar that was causing the blockage.


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Thanks man... I'll bet you are right!