Another 5th gen rear brake problems

Hello from a very wet n windy UK.
Ive been trying to get my first VFR on the road ready for spring but have fallen at the last hurdle.
I've done the front brakes and am happy but its the back I'm having problems with.
I get good pressure on the pedal and when I spin the back wheel it stops dead as it should
but after a short while the pressure fades and the brake won't stop the wheel.I need to pump
the pedal 4or so times to build pressure to stop the wheel again
All the bolts are tight and no leaks from the system . I'm pretty sure I've not got air in the system
so am scratching my head. Any help will be greatly appreciated

 

To bleed the rear you have to bleed the front calipers, the valve behind the tank, and the rear caliper.
Did you do them all?

 

Yes , I did as described in the Haynes manual.I bled the hell out of them and got good clear
fluid with no bubbles
The rear lever goes hard and feels good but then looses pressure after about 5 mins and goes soft
with no pressure and no braking . Then pump ,pump ,pump and it goes hard again.

 

Sounds like the rear brake master cylinder is leaking internally. If so, rebuild or replace.

 

^^^^^^^^^^^^^^^What he said.

 

Thanks fro the replys,that's what I thought. I've pumped the pedal again and get a squeaking
noise from the front left caliper. Is that normal ?
When I took the smc to bits to clean I found the actuator rod to be a sloppy fit.
Is that normal as well . Didn't know if that needs rebuilding ?

 

Bought a repair kit and will rebuild when I get some time.
Went for a sneaky ride today and can see why you guys like Vfr s
The sound from that engine is just awesome !

 

That squeaking at the front left is the secondary master cylinder most likely. When pressing the rear pedal, it pushes fluid into the SMC. You might want to check it out as well as this could be affecting your line too. I've seen a couple of post, one here and on VFRD where the SMC needed to be rebuilt/replaced. Also one in regards to the rear PCV being bad.

 

Got the rmc rebuilt and has sorted my problem, brake nice and solid now.
A big thanks for the replys oz vfr, mastershultz,fj 12 rydertoo and ootv.
The smc still squeaked but not as much so I packed red grease under the rod and boot.
Cheers

 

Heya!
Got kinda same problem I think.
My rear brake pedal operates from normal to zero in a few rides. Brake fluid level stays same. So - system sucks air somewhere I think.
I head squacking sound from front left caliper then using pedal or bleeding brakes with pedal too.

All brakes where fully rebuild past winter actually. All Pistons polished, all piston seals new. Also repair kit for front master cylinder.
But! I have cleaned secondary master cylinder too, and got one rubber seal (outer one) cut by accident. So I have replaced it with one used from front master cylinder (same inner/outer size of seal and same size of place on piston where it fits - so I was thinking it's good to go. But seals have some difference in shape...)
One of banjo bolts was leaking month ago also, had to replace it (rear brake line).

So... I think problem could be in secondary master cylinder seal, which has wrong front master cylinder seal. Or in other banjo bolts (few of them had sings of use), and I have to replace all 6 for rear line. Or... What else? Maybe hard line on forks? It doesn't even have any seals in it, so maybe I need to tighten it somewhere or something.

I have disassembled everything, except rear master cylinder when rebuild all. So my fault can be anywhere.

Did another smc inspection and bleed all rear line, brakes are superb after 30km ride. But they will become poor again soon I think...

 

Well, brakes were superb, but I think they are dragging( rear rotor was really hot after a ride back without using rear at all/small use of front. Hot - can't hold finger more than 1 second.
Spent 80$ (cry) on SMC Honda repair kit, new piston and push rod. Sits perfectly now, works good, all brake lines bled by ultimate manual too.
What in result? Damn it, rear rotor gets hot again( front - just warm.
I think I returned to my first problem past autumn - this dragging eated my rear pads to metal - from this my story starts.

Any suggestions?
1) I noticed that pipe from brake fluid reservoir has poor connection to RMC. It is tightened good, but I can see a hole in upper part - sits unperfectly. Could cause air in brakes? Yes. Could cause dragging? Don't think so.
2) Brake pads retaining pin? I've read few comments about it on the web. Didn't touch it, but it could cause dragging. Will check.
3) Faulty LPCV? How can be sure? Everything is good with it in part of bleeding.

Also, pushing SMC with rear brake uninstalled shows that center piston is moving as it should, releasing the pads.
Didn't check other pistons, but I think they are operating good too - full rebuild was done remember?
Will also try to experiment with wheels free spin - didn't do because don't have center stand.

Please post some comments, this thing drives me crazy.

 

You might check the fluid return hole in the rear master cylinder. Make sure you don't have a little crud in there that is not allow for full release of fluid back to the master cylinder.

 

As FJ says, tiny bleed hole in the MC most likely blocked

 

Ok thanks, i will check everything today. Can't even sleep normally because of this mad thing. Holidays are over, but i will have to spent time after work with flashlight
I have checked RMC in past and it was kinda ok. Didn't have cleaner spray to clean it good (all gone on calipers), so maybe it needs some more love.

But how could brakes bleed normally, so this tiny hole is working, but it get's stuck when i ride?
And how could it be, that brakes operate from "no rear brake at all" to "rear brake dragging" ? What could cause this?

Will:
- Diassebmle RMC and clean it
- Screw hose from reservoir to RMC correctly
- Will check free wheels spin with jack-screw
- Will check pistons moving with rear\front brake - do they return when i release brake
- Will check Brake pads retaining pin
- Do full bleed again, because after RMC off - air will get into system. Do i need to go full bleed or only via LPCV under seat? This one is closest to RMC and could do all job. Or do rear caliper too? Do i need to do SMC bleed too?

 

I'll try to restore full story from the start (Autumn 2014).

- My rear brake started dragging (i thinked so), and it ate rear pads to metal (rotor has suffered a bit too, some grooves appeared on disk).
- I have bought LMC rebuild kit, rubbers for all 9 pistons. Rebuid all calipers and LMC. Pistons were polished to mirror like condition. Calipers cleaned from rust and dirt.
- After full assembly and bleeding my brakes started dragging a lot so bike could not ride at all. This was first fail - i have failed on installing PUSH ROD from Front lever to LMC. Wrong push rod direction I didn't know about that so:
- I did full rebuild again, full clean. Plus SMC check. Assembled again. Same result.
- Another full rebuild. Another SMC check - i have broke SMC piston seal (outer one). Replaced it with old seal from LMC (outer one too), it was almost same in form, and totally same in size. Could be fail?
Plus i have blew all brake hoses with air (to push any dirt). Metal brake lines (between front fork) and servo valve (or right fork) were taken off and blewed too. Can't be sure i have assembled them correct, those metal things don't even have any rubber seals on them.
- All this didn't help, but then i realised about Push rod (thanks to VFRWorld forum) and i was able to ride.
- Rear brake started to become poor and poor again till it almost disappeared. Season 2014 was almost over in November.

- Spring 2015, new season. Did full bleeding. Rear brake started dragging a bit. Went to bike service, told them everything. They have opened RMC reservoir and hey - they don't drag anymore! Pure magic. Then we did full bleed together again (good Honda service, but they didn't even know how to do full ultimate bleed lol).
We have also installed other used rear brake pads (Nissin blue ones), to grind rear rotor a bit (blue pads are hard).
- I've been riding normally for 2 months, then my rear brake line started bleeing from Banjo bolt (rear line on right caliper). So rear brake started to disappear.
- I have replaced 2 Banjo bols and washers and bleeding has stopped. I have also intalled back rear Honda soft pads. And again - full brakes bleeding.
- Rear brake almost disappeared in 4 days of riding.
- Another full bleeing, rear brake disappeared in 2 days.

- 2 days ago: SMC check, full bleeding. All rotos get hot, rear - really hot.
- Yesterday: SMC full rebuild kit, after remembering that i used seal from LMC and this could be fail.
Full bleeding. Plus, i have used superglue (yeah swear on me) to close gap between hose from reservoir and RMC. Brakes dragging again, rear rotor hot.

 

Another thing i'm thinking about is method of brakes bleeding.
Is that permissible to bleed rear (or any) brake with nothing installed between pads? Rear caliper isn't on rotor when bleeding. And i'm sure i didn't use anything last times to hold the pads.
That means - bleeding was done with pads compressed to each other. All 3 pistons are out. Then i spread pads moving pistons back to caliper. Then install caliper on bike.
Considering complexity of LBS and lenght of brake magistral... This pistons spread could cause additional pressure in system (for example, brake fluid is compressed a bit), so when i install caliper and use brakes - this pressure holds brake ON even without applying rear brake.
Or maybe moving pistons back doesn't create enought pressure to get brake fluid back to reservoir through small holes and all system and it just compresses in hose. Same result.

Am i right? I think i need to check everything and also do bleeding with some "rotor-like" installed between pads.

Another reason to belive in this theory is - another result of brakes bleeding in past, in moto-service - brakes didn't get lock after this bleeding. Can't remember if we used something to put between pads. But such bleeding resulted into "No rear brake" after 2-3 days
Hmmm, "No rear brake" maybe was caused by fail in SMC, which is fixed now. So correct bleeding could solve all problem.

Please tell me am i right? No? Yes? Omg(((

 

I have done the bleeding several times on 2 different generation VFRs with linked brakes and it was only the last time I did it that I actually put something between the pads to keep them from closing all the way. I did this not to prevent any problems but to make it a little easier to open the pads a bit more when putting the caliper back onto the rotor.

I'll be honest I have not read all of your thread but it sounds like the only thing that has not been touched and/or replaced is the proportional control valve. Maybe that is what is contributing to problem? There was a test that someone did that helped point to this being the culprit with their issue but I'd have to really go and dig through the archives to see if I can find it. I don't recall if the Honda service manual has a testing procedure for this either.

 

Are you CERTAIN the return hole to the M/C is clear? Because that's exactly what it sounds like....

 

Did you fill the M/C after you bled the system? If you had the pistons fully out and then filled the M/C, and then moved the pistons back into the caliper, perhaps you have an overfilled M/C.

 

Found what I was looking for, albeit on a different forum, but here's that thread...

http://www.vfrdiscussion.com/forum/...nd-pad-pins-98-vfr800/?hl=havagan#entry894499

And +1 to what FJ12 said. If you filled it to the max line and then opened the caliper, you could have pushed the level beyond maximum. I usually bleed them with the rear off the rotor, as per the manual, then once the caliper is back on the rotor, I give it a few more bleeds just to make sure the level isn't too high. The left front I do similarly, as the manual calls for taking this off the bike too. So once it's back on the bike, it's part of the final button up bleed process for me.