Honda VFR 800 6th gen right brake caliper prob (sticky operation)

[justsky]

Hello there,

today when I put my bike on the centrestand I've spotted that the front wheel doesn't rotate as it should (it seemed that one of the front calipers remains slightly blocked). After having removed brake pads I separated the right caliper from the caliper bracket.

When I applied some pressure on the front brake lever two pistons moved slightly (I could both see it and feel it when I held my fingers inside the caliper housing), but the third one seems to be blocked. I tried to move it applying some force on it but it didn't move anywhere.

Now my question is:

Are there any ways to solve this problem other that disconnecting the banjo bolt, overhauling the caliper, cleaning it and bleeding the brake system?

I don't have any bleeding tools at hand and I wonder if it might still be possible to overhaul the caliper without disconnecting the banjo connector.

Your advices are very appreciated.

Andrey

[2FAST4U]

Hello there,

today when I put my bike on the centrestand I've spotted that the front wheel doesn't rotate as it should (it seemed that one of the front calipers remains slightly blocked). After having removed brake pads I separated the right caliper from the caliper bracket.

When I applied some pressure on the front brake lever two pistons moved slightly (I could both see it and feel it when I held my fingers inside the caliper housing), but the third one seems to be blocked. I tried to move it applying some force on it but it didn't move anywhere.

Now my question is:

Are there any ways to solve this problem other that disconnecting the banjo bolt, overhauling the caliper, cleaning it and bleeding the brake system?

I don't have any bleeding tools at hand and I wonder if it might still be possible to overhaul the caliper without disconnecting the banjo connector.

Your advices are very appreciated.

Andrey

That's how it was designed to work.

Your bike has linked brakes. When you pull the front brake lever, it operates the outer pistons in each of the front calipers and the inner piston in the rear caliper. When you push on the rear brake pedal, it activates the center pistons in each of the front brake calipers and the outer pistons in the rear caliper.

When was the last time your brake system was bled? It's supposed to be done every couple years. If you can't remember, now may be a good time to do it.

As for what's causing the front wheel to not rotate properly, it could be that a brake pad got loose (I've seen that.) You could also have a warped disk (but that's not likely.)

[justsky]

Sorry. May be I wasn't clear enough expressing myself. I know about the feature called DCBS (dual combined braking system) you have just mentioned.

My problem is that the third piston (i.e. top piston) on the right caliper (not 2nd on the left caliper!) is permanently in its expelled position which causes the corresponding brake pad to come in contact with the brake disc which in turn, results in the front wheel being slightly blocked all the time.

Since I don't have any bleeding tool available, I wonder if there's another way to fix this without overhauling the caliper and bleeding the front circuit of the braking system.

And yes, the braking system has been bleed by the Honda dealer before I bought it last month.

Andrey

Hello there,

today when I put my bike on the centrestand I've spotted that the front wheel doesn't rotate as it should (it seemed that one of the front calipers remains slightly blocked). After having removed brake pads I separated the right caliper from the caliper bracket.

When I applied some pressure on the front brake lever two pistons moved slightly (I could both see it and feel it when I held my fingers inside the caliper housing), but the third one seems to be blocked. I tried to move it applying some force on it but it didn't move anywhere.

Now my question is:

Are there any ways to solve this problem other that disconnecting the banjo bolt, overhauling the caliper, cleaning it and bleeding the brake system?

I don't have any bleeding tools at hand and I wonder if it might still be possible to overhaul the caliper without disconnecting the banjo connector.

Your advices are very appreciated.

Andrey

That's how it was designed to work.

Your bike has linked brakes. When you pull the front brake lever, it operates the outer pistons in each of the front calipers and the inner piston in the rear caliper. When you push on the rear brake pedal, it activates the center pistons in each of the front brake calipers and the outer pistons in the rear caliper.

When was the last time your brake system was bled? It's supposed to be done every couple years. If you can't remember, now may be a good time to do it.

As for what's causing the front wheel to not rotate properly, it could be that a brake pad got loose (I've seen that.) You could also have a warped disk (but that's not likely.)

[2FAST4U]

Now I understand. I don't know why that piston is stuck.

If I were you, I'd remove the brake pads again and push in all pistons in your front brake calipers. Do not pull on the brake lever yet. Now reassemble everything and take the bike around the block (using the front brake lever to slow down or stop.) If that same piston gets stuck again, I don't know what to tell you.

I'm sure somebody here might know.

[justsky]

The problem is that this piston doesn't move in any direction, since it's simply stuck. So far I don't see any solution alternative to the one suggested by my Haynes manual which suggests disconnecting the banjo screw, completely removing the caliper, cleaning it and bleeding the breaking system later.

Let's wait a bit and see what other more experienced bikers will say.

[Monk]

You might try using some force(if you haven't already), to try and push it loose(if a fluid port isn't clogged). In some cases people don't clean around the piston area while they have the pads out.

[justsky]

Thanks John!

I tried to apply some force but didn't manage to move the piston (the gap between the two parts of the caliper is too small which makes it difficult to use any tool as a lever for applying force).

It seems that it will be easier to overhaul the whole caliper, clean it properly and bleed the braking system. Nevertheless, every cloud has its silver lining! I will finally learn how to bleed the breaking system which I wanted to avoid by any means

[mello dude]

You might try unbolting the caliper and use a good size C-clamp to try to get the piston to move.

[justsky]

You might try unbolting the caliper and use a good size C-clamp to try to get the piston to move.

Thanks a lot dude . That's a good point, actually. It might be a tricky task to expel the blocked piston though, but having moved it once by means of a C-clamp in at least one direction may help to avoid a lot of hassle.

[2FAST4U]

You don't have to use a C clamp. Anything long and narrow (that isn't sharp at the tip) would work.

[vfrjim2002]

I recommend NOT pushing the piston back in until you've cleaned it. On the right front all three pistons are actuated by the front MC. Take the pads out, operate the front MC to push out the pistons, NOT all the way just a bit. If only one or two move, use a c-clamp or equivalent to hold the movers in place while you press the stuck piston out. Once you see about 1/4 inch of clean piston exposed, use a piece of scotch-brite or emery cloth to clean the piston. It's tight, but doable. Then, and only then, push the piston back into the caliper.

If the piston is really stuck - the only way to generate enough force to get it out is the MC. Compressed air (at least at 90psi) usually won't do it. So, if you do end up rebuilding the caliper(s) there's no point in taking the caliper off before you get the pistons out. If you end up taking this route, make sure you clean the caliper bores and seal/scraper grooves really well and install new seals and dust scrapers. Scotch brite, emery cloth or crocus cloth and a pick will do wonders for the clean up. While you're at it, polish the pistons with the same stuff. ONce you get it all back together the only thing you need to bleed the brakes is fluid and a 12 - 16 inch piece of clear tubing. No fancy schmancy vacumn pumps required.

good luck.

[Cogswell]

I recommend NOT pushing the piston back in until you've cleaned it. On the right front all three pistons are actuated by the front MC. Take the pads out, operate the front MC to push out the pistons, NOT all the way just a bit. If only one or two move, use a c-clamp or equivalent to hold the movers in place while you press the stuck piston out. Once you see about 1/4 inch of clean piston exposed, use a piece of scotch-brite or emery cloth to clean the piston. It's tight, but doable. Then, and only then, push the piston back into the caliper.

If the piston is really stuck - the only way to generate enough force to get it out is the MC. Compressed air (at least at 90psi) usually won't do it. So, if you do end up rebuilding the caliper(s) there's no point in taking the caliper off before you get the pistons out. If you end up taking this route, make sure you clean the caliper bores and seal/scraper grooves really well and install new seals and dust scrapers. Scotch brite, emery cloth or crocus cloth and a pick will do wonders for the clean up. While you're at it, polish the pistons with the same stuff. ONce you get it all back together the only thing you need to bleed the brakes is fluid and a 12 - 16 inch piece of clear tubing. No fancy schmancy vacumn pumps required.

good luck.

It's really worth it to understand why the piston is sticking in the first place. The added benefit of bleeding your own brakes is that you can change the fluid every few years and most likely never have this problem again. I change my 5th gen's every 2 years and I've never had an issue. (I do wimp out though and use a vacuum bleeder )

ps - brake fluid will tear the hide off your paint job, so be sure to cover (or remove) the fairings, front fender, tank etc well while the M/C cover is removed. All you have to do is bump the bars or front wheel while it's open and brake fluid will go everywhere.

[justsky]

Thanks a lot guys! Everything you've suggested sounds to be true and very logic. I'll do this job at the coming weekend and will let you know about my progress (of course if this thread won't be deleted by that time).

To Cogswell :

Do you think this problem I have could be caused by an irregular change of the DOT fluid done by the previous owner? Can it just be a result of contamination and/or high temperatures?

Cheers!

Andrey

[kaldek]

Here's how I would budge that piston:

• Take out the pads
  
• Put a block of wood behind the working pistons, but not the stuck piston
  
• Work that front brake lever!
  

This should put all force on that stuck piston and get it moving. Be prepped in advance - buy new piston seals at the very least. I have an entire drawer full of all the parts needed for a full caliper rebuild on the front and rear calipers on my 2002 - including the piston seals and all the dust and grease boots! No expense was spared!

All I have to do now is get organised to just do the work...

[SEBSPEED]

I recommend NOT pushing the piston back in until you've cleaned it. On the right front all three pistons are actuated by the front MC. Take the pads out, operate the front MC to push out the pistons, NOT all the way just a bit. If only one or two move, use a c-clamp or equivalent to hold the movers in place while you press the stuck piston out. Once you see about 1/4 inch of clean piston exposed, use a piece of scotch-brite or emery cloth to clean the piston. It's tight, but doable. Then, and only then, push the piston back into the caliper.

If the piston is really stuck - the only way to generate enough force to get it out is the MC. Compressed air (at least at 90psi) usually won't do it. So, if you do end up rebuilding the caliper(s) there's no point in taking the caliper off before you get the pistons out. If you end up taking this route, make sure you clean the caliper bores and seal/scraper grooves really well and install new seals and dust scrapers. Scotch brite, emery cloth or crocus cloth and a pick will do wonders for the clean up. While you're at it, polish the pistons with the same stuff. ONce you get it all back together the only thing you need to bleed the brakes is fluid and a 12 - 16 inch piece of clear tubing. No fancy schmancy vacumn pumps required.

good luck.

^^ What he said!

[Cogswell]

Thanks a lot guys! Everything you've suggested sounds to be true and very logic. I'll do this job at the coming weekend and will let you know about my progress (of course if this thread won't be deleted by that time).

To Cogswell :

Do you think this problem I have could be caused by an irregular change of the DOT fluid done by the previous owner? Can it just be a result of contamination and/or high temperatures?

Cheers!

Andrey

I'm not sure what you mean by an irregular change - if that means infrequent (such as just once or never), I suppose my answer would be 'possibly'. If it was never, there's a good chance that over many years moisture has collected in the fluid (actually over 8 years almost certainly). DOT 3&4 fluids are hydroscopic, meaning they attract and will absorb moisture from the air. Especially if it's spent a lot of time in a humid climate, or ridden in the rain a lot, it's very possible the moisture corroded the interior of the bore or the piston causing increased friction and thus sticking. The additional downside to moisture contaminated fluid is that it lowers the boiling point, reducing braking performance. One time I changed the brake fluid on an ex G/F's car and what came out of the calipers looked like Thanksgiving gravy. The combination of the water in the fluid and thousands of heat cycles had broken it down to a brown goo. The Viffer's braking system likes clean, fresh fluid. Also, DOT 5 silicone fluid is not compatible with DOT 3&4 fluid. Silicone fluid will not absorb moisture but should not be used in your VFR. Stick with DOT 4 fluid every 2 or 3 years and the only brake service you'll probably ever need to do is to change out the pads. If you take the caliper apart and you have corrosion on either the piston or particularly in the bore that cannot be polished out to an nice even finish, best to replace it. And if you have it in one caliper it's probably also in the others - in that case it would be good to inspect those as well. There was a brand new 6th gen OEM front caliper on ebay last week - I don't recall which side. I do use a vacuum bleeder because it prevents the old fluid expelled from being drawn back up in to the caliper. It is a one way deal, with only clean fluid coming down from the master cylinder so I get 100% new fluid in the system. While you're at it, It's also a good idea to change the clutch fluid as well. Best of luck with your project.

[justsky]

Thanks mate! Now I see where the problem lies and will try to fix it tomorrow. It won't be a surprise if that caliper piston bore with blocked piston in it is rusted also. I have a 450ml big WD-40 spray and hopefully it will help me.

[justsky]

Done! It turns out that the upper piston on the right caliper was stuck. I cleaned all the three pistons and receiving cylinders using WD-40. After assembly I bled the system and tested brakes on the road.

My only concern is the fact that when I've put my bike on the centrestand and tried to rotate the front wheel I've noticed that it doesn't rotate freely but there was some friction caused by the brake pads.

Is it OK or should the front wheel rotate with no friction at all?

[Cogswell]

I have my 5th gen on stands doing some maint - so I went out and noted the location of the F wheel valve stem and gave the wheel several spins. Not mega hard, just a firm hand on it. It went about 1 1/4 to 1 1/2 turns each time before coming to a stop. I do hear the pads contacting the rotors, but it's just a very slight. If you can't make the wheel do at least 1 turn after you spin it, you probably have too much. You could remove 1 caliper at a time and see if one is creating more than the other - then take both off and compare with how many revs the wheel does without the calipers at all. It shouldn't be very much difference. Something like 1 1/2 to 2 turns w/o calipers and less than a full turn with them on is probably too much difference. Do it 5 or 6 times to average it out and see what you get. You also might check the service manual to see if there's a spec on drag and how to measure it. Maybe someone here's done that or knows of a better technique.

[justsky]

I have my 5th gen on stands doing some maint - so I went out and noted the location of the F wheel valve stem and gave the wheel several spins. Not mega hard, just a firm hand on it. It went about 1 1/4 to 1 1/2 turns each time before coming to a stop. I do hear the pads contacting the rotors, but it's just a very slight. If you can't make the wheel do at least 1 turn after you spin it, you probably have too much. You could remove 1 caliper at a time and see if one is creating more than the other - then take both off and compare with how many revs the wheel does without the calipers at all. It shouldn't be very much difference. Something like 1 1/2 to 2 turns w/o calipers and less than a full turn with them on is probably too much difference. Do it 5 or 6 times to average it out and see what you get. You also might check the service manual to see if there's a spec on drag and how to measure it. Maybe someone here's done that or knows of a better technique.

Hmm...that's something I don't understand quite well. If I apply force on the front brake lever the master cylinder creates hydraulic pressure which in turn makes brake pistons to expel and apply this force on the surface of the brake pads. What happens next when I release the brake lever? I think that the hydraulic pressure drops and some of hydraulic liquid flows back to the master cylinder reservoir, but since there is no counteracting force which spreads the brake pads and brake cylinders to their retracted position they remain in a slight contact with the brake discs even when you don't brake.

I checked the caliper and the brake disc and they both weren't hot even after 40 mins of riding which means that the residual friction isn't that big and is within the limits. Am I right or I still don't understand something?

[Mohawk]

Well there's definately something you don't understand & that is how the brake caliper pistons work. The main seal is just a square section seal, but the groove it lives in is NOT, it is shaped like this /¬\ such that when the piston moves it compresses or deflects the seal in the direction of travel, when you release the brake the seal returns to its undeflected shape & pulls the piston back from the brake pad creating the clearance to allow the disc relatively unhindered travel.

The seal retraction only provides about .5-1mm retraction, which is why opposed piston calipers don't drag as much as sliding ones !

Some nice diagrams at the bottom of this PDF. http://www.simulia.com/download/solutions/automotive_cust%20references/brakes_analytical_auc03_delphi.pdf

[Switchblade]

I recommend NOT pushing the piston back in until you've cleaned it. On the right front all three pistons are actuated by the front MC. Take the pads out, operate the front MC to push out the pistons, NOT all the way just a bit. If only one or two move, use a c-clamp or equivalent to hold the movers in place while you press the stuck piston out. Once you see about 1/4 inch of clean piston exposed, use a piece of scotch-brite or emery cloth to clean the piston. It's tight, but doable. Then, and only then, push the piston back into the caliper.

If the piston is really stuck - the only way to generate enough force to get it out is the MC. Compressed air (at least at 90psi) usually won't do it. So, if you do end up rebuilding the caliper(s) there's no point in taking the caliper off before you get the pistons out. If you end up taking this route, make sure you clean the caliper bores and seal/scraper grooves really well and install new seals and dust scrapers. Scotch brite, emery cloth or crocus cloth and a pick will do wonders for the clean up. While you're at it, polish the pistons with the same stuff. ONce you get it all back together the only thing you need to bleed the brakes is fluid and a 12 - 16 inch piece of clear tubing. No fancy schmancy vacumn pumps required.

good luck.

^^ What he said!

Did the pads that came off not wear funny ?