800 FI-W rear brake centre pot problem!!

Hello all, I have a 800 FI-W with the linked front- back brake, the bike has been sitting for two years and know its back on the road but, i put new brake pads in both front and back and now im having trouble with the rear brake binding, on investigation iv found that its the center pot (front activating) of the rear caliper that moves freely but when pushed via the front secondary master acting via the front brake it doesn't return taking the pressure off of the pads, do i have a problem with the compensator valve or is it just me being daft, any help would be nice
Robin

 

Funny that I have a 2000 VFR (5th generation) brake system with exactly the same problem. I have searched the forums for an answer to the problem and all I find are lots of people with the same issue and no solution. Surely some one has figured out what causes this and can help us. This bike had new pads and fluid change. we bled the system as required in the service manual. We have dis assembled and cleaned the rear master cylinder and rear caliper (all of which seemed fine) and rebled the system and still the rear caliper, (center piston) is binding. That is to say it works but acts as though the pressure is not being released from it. The rear wheel becomes very hard to turn and the rear disc gets very hot very quickly. We probably have 10 hours in this thing and have reached the point of frustration. Any one know if the pcv valve under the rear of the tank has a return that clogs or if the delay valve on the front right fork is the problem.

 

Also need to mention that all calipers are clean and working and all floating parts have been cleaned and lubed so there is no mechanical binding of the caliper. The problem seems to be in most all of these issues fluid pressure not being released. The rear master cylinder has also been adjusted properly as to not be actuating the rear caliper until the pedal is depressed. All hoses looked good with no cracks or buldges. I am out of ideas. Help!!

 

Robinday, I have the answer to your problem. We just figured it out after many hours of work and re work and new parts and here goes!! The VFR uses two different brake pads for the front and the rear. It is a very small but very important difference and the problem is aftermarket brake pads are all the same. The rear brake pad must have a small slot cut into the mounting tab opposite the end with the hole. That tab slides on a ridge in the metal mounting insert that clips into the rear caliper. If you use pads without the gap cut into them they hang which is what happened to me, you and a dozern other people who have placed similar posts with no answer.

 

Also, and not to over-simplify, but be certain that the fluid reservoirs sre NOT full!!
Run them at the marker..no more than half-full..check this 1st! just sayin'..my 2cents!

 

All the fluid in the world is not an issue if the pads need a groove that is not there.

 

Funnily enuf, i just spent the last 6 weeks trying to get aftermarket pads with the grooves cut in them for the rear caliper and after 2 arguments with vendors who thought i hadn't a clue i got em! Goldfren are the make!
My question before i give advice is how cud u have gotten the pads with no slot onto the caliper?-there is no room unless you beat them on with a lumphammer?
I've had this problem in the past, it's always either
1.-the seal for that piston is in poor condition and not allowing the piston to slide back.

2. The sliding pins have no red rubber grease in them/are seized and are giving the false impression that the piston is sticking once the caliper is mounted(they won't slide back when the caliper is free from the disc!

3.- The piston has some pitting and is catching on the seal and stopping it from returning.

 

I concur with your findings fellow-Rider! Do you know that some VFR's are coming into shops with over-filled brake fluid reservoirs?
Do some quick calculations(temp./hose age/expansion) and an in-experienced Viffer could lay out big $$$ without having looked here first!
Thanks for pad data/info! Cheers!

 

That's the problem

The pads without the grooves will easily install in the rear caliper. The ridge is very small that the groove rides in. When we installed the pads without the groove you felt a very small amount of "spring like" pressure as you push the pads in place to insert the retainer or locator pin. (what ever you want to call it) Anyway, they easily install and they will work and SLIGHTLY release but they do stick and heat up and then cause all kinds of problems. I know this has happened to dozens of VFR riders because I searched for answer to my problem and many people including the person who started this thread have had the same problem but no one had posted a solution to it. All the things you mention and an un clean floating mechanism can cause this type of issue but the UN GROOVED PADS are definately the culprit in a lot of these issues. You yourself said even the vendors don't know about the difference. We bought the un grooved pads from a Honda shop. They should know better!!!

 

Agreed but i really had to force the ungrooved pads on and that rang alarm bells for me. The grooved ones have about a 10mm cut in them which means you have to jamm the retaining pin in at an angle to get them on there. No one believed me but if you go onto the fiche for the rear brake from Honda you can actually see the rear pads have grooves cut in them, but for that no one would listen. Yea Honda should know better!