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Discussion Starter #1 (Edited)
Hello everyone,

I have a 2000 VN 750 that I have recently brought back too life. I am needing to either replace/rebuild the front calipers and was wandering what the community suggested? I am hoping to rebuild the calipers as it is cheaper but have not found any good resources on the rebuild process and was wandering if anyone had a video or instructions to get these calipers open?
 

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Usually, the caliper piston is pushed out by putting compressed air through the hole for the brake line.

Check YouTube, should be some video there, may not be specific for the Vulcan, but most assemble the same way.
 

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Usually, the caliper piston is pushed out by putting compressed air through the hole for the brake line.

Check YouTube, should be some video there, may not be specific for the Vulcan, but most assemble the same way.
Hi, glad to have info here on everything, and glad the Spockster is on the case. :)

I have a photo of my brake caliper all exploded, except for the piston.
52758


Here's what I ran into:

1. The black caliper pins bracket would not push back into the caliper far enough to let the outside brake pad slip off. I found that the rubber boots were starting to degrade and were leaving rubber deposits everywhere. So I cut them off since they have to be replaced. Then I saw the circled brake pad stopper was hitting the caliper piston cylinder. Pushing it back with a screwdriver then gave me just enough room to push the pins bracket back a few more mm.

2. Lots of fluid will squirt out if you push back the piston at this point. I used a C-clamp to push it all the way in to test movement and push out fluid. Also, when you remove the bleeder valve, the rest of the fluid will pour out. Be ready.

3. There is a thin strip of teflon tape on the bottom threads of the bleeder valve. Made a note for re-assembly.

4. Will have to order new crush washers for the banjo bolts.

5. The brake pads are re-usable, have 5/32" (4mm) thickness left and were evenly worn and not glazed. I liked the look of the stock Tokico pads; they seemed metallic which I like (I use EBC Sintered if I want a very hard bite, Ferodo for gnarly stopping power, do not enjoy the characteristics of ceramic pads). But the brake backing plates are rusted pretty bad and should be sanded smooth if I reuse them.

6. Gotta pop the piston out. Will swing by the cycle shop or a mechanic friend and hope that compressed air in the brake line hole will pop it out. Guess I'll have to put back the bleeder screw. I've seen some guys who leave the caliper connected to the brake hose. They pull out the pads and then pump the brakes to let the fluid push the piston out.

But if you have a plugged/messed up caliper like mine/ours compressed air is supposed to work. Have you tried it yet?

7. The outer edge of the piston is rusted. Hope this doesn't come into play, and the rest is smooth and will move easily. I'm pretty sure the piston cylinder seals will need replacing. Manual shows one at front and one at back. I don't know what that black plastic disk is on the piston face. It rotates freely on one caliper and is stuck on the other.

Hope all can be refurbished without replacing piston/caliper, for sure.
 

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Hi, glad to have info here on everything, and glad the Spockster is on the case. :)

I have a photo of my brake caliper all exploded, except for the piston.
View attachment 52758

Here's what I ran into:

1. The black caliper pins bracket would not push back into the caliper far enough to let the outside brake pad slip off. I found that the rubber boots were starting to degrade and were leaving rubber deposits everywhere. So I cut them off since they have to be replaced. Then I saw the circled brake pad stopper was hitting the caliper piston cylinder. Pushing it back with a screwdriver then gave me just enough room to push the pins bracket back a few more mm.

2. Lots of fluid will squirt out if you push back the piston at this point. I used a C-clamp to push it all the way in to test movement and push out fluid. Also, when you remove the bleeder valve, the rest of the fluid will pour out. Be ready.

3. There is a thin strip of teflon tape on the bottom threads of the bleeder valve. Made a note for re-assembly.

4. Will have to order new crush washers for the banjo bolts.

5. The brake pads are re-usable, have 5/32" (4mm) thickness left and were evenly worn and not glazed. I liked the look of the stock Tokico pads; they seemed metallic which I like (I use EBC Sintered if I want a very hard bite, Ferodo for gnarly stopping power, do not enjoy the characteristics of ceramic pads). But the brake backing plates are rusted pretty bad and should be sanded smooth if I reuse them.

6. Gotta pop the piston out. Will swing by the cycle shop or a mechanic friend and hope that compressed air in the brake line hole will pop it out. Guess I'll have to put back the bleeder screw. I've seen some guys who leave the caliper connected to the brake hose. They pull out the pads and then pump the brakes to let the fluid push the piston out.

But if you have a plugged/messed up caliper like mine/ours compressed air is supposed to work. Have you tried it yet?

7. The outer edge of the piston is rusted. Hope this doesn't come into play, and the rest is smooth and will move easily. I'm pretty sure the piston cylinder seals will need replacing. Manual shows one at front and one at back. I don't know what that black plastic disk is on the piston face. It rotates freely on one caliper and is stuck on the other.

Hope all can be refurbished without replacing piston/caliper, for sure.
Been a long time waiting for parts. In the meantime I had the brake piston frozen in the left caliper. The right came out easily with 35psi of compressed air. But the left will not come out even after soaking.

I was going to use my master cylinder to press it out. The master cylinder was frozen so I disassembled it and cleaned it thoroughly with isopropyl and blew through the two holes and all was clear. Re-assembled it and hooked up a brake line to the left caliper. But it would not pump up. Concerned that the rubber seal in the MC piston was deteriorated, and busy with holidays, so I was lazy and took it to my dealer and asked him to check the MC and use it to press out the stuck piston. They charged me $60 for my laziness; lesson learned

A hint. If you have fully drained your system there may be too much air for it to pump up. You will have to take steps to remove air before you connect the brake hoses. I read that people use their thumb to cover the MC hole and bleed it, and then do the same with the end of the hose. I have a Mity-Vac so that should do the trick; again I was just being lazy and spoiled myself but no more...

Anyway, here is my question of the day: What is the purpose of the black plastic cylinder that is inserted inside the hollow brake caliper piston?

Because it comes out freely and rotates freely in my right brake piston, but is frozen in place in my left caliper piston. I can probably clean up the piston surface with wet-dry and 3M buffing pads, but is this frozen black cylinder on the piston face going to cause problem?

Photo attached. Thank you for your insights.
52764


52765
 

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Anti-rattle is the best I can come up with for the black part.
 

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UPDATE:
Used All Balls Racing caliper rebuild kit which comes with brake piston inner and outer seals, pin guide rubber boots, bleed valve cap and two copper crush rings $40 for both calipers.
52827

Wish it had pistons because my left one was all pitted, so I bought a piston from K&L for about $30 ouch.

Anyway, when I put in the seals the pistons were very tight and did not slide in the bores easily. I forced them in and they moved and retracted when I pressed the brake lever, but I felt bad about how tight they were. I researched on here and online and found that the brake piston seal grooves should be very clean. Mine were full of crystalized brake fluid and hardened black rubber from the old seals.

I had used a small flat blade screwdriver to scrape out the grooves. Anyway, I decided to do it now instead of later so I pulled the calipers apart again. I used the brakes to pump out the piston, then grabbed it with padded pliers and was able to extract it. I will use Dremel tool to polish and clean the grooves to make them more like new.

Reason for posting:
I noticed that the new brake fluid in the bore had tinges of black. When I cleaned the new rubber seals, black residue came off on the paper towel. Bothersome. Brand new rubber seals should not easily decompose in clean brake fluid?

Should I be concerned and not be keen on All Balls rubber seals?

52828
 

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Anti-rattle is the best I can come up with for the black part.
UPDATE: I did verify when working the brake lever that the black hardened plastic cylinder inside the brake piston bore does move independently from the piston itself.

So being frozen is probably not a great thing. Anyway, after soaking in Liquid Wrench for two days, mine came unfrozen.

But I decided to go full quality, and because the piston itself has pitting, I am replacing it.
 

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2001 Kawasaki Vulcan 750
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UPDATE:
Used All Balls Racing caliper rebuild kit which comes with brake piston inner and outer seals, pin guide rubber boots, bleed valve cap and two copper crush rings $40 for both calipers.
View attachment 52827
Wish it had pistons because my left one was all pitted, so I bought a piston from K&L for about $30 ouch.

Anyway, when I put in the seals the pistons were very tight and did not slide in the bores easily. I forced them in and they moved and retracted when I pressed the brake lever, but I felt bad about how tight they were. I researched on here and online and found that the brake piston seal grooves should be very clean. Mine were full of crystalized brake fluid and hardened black rubber from the old seals.

I had used a small flat blade screwdriver to scrape out the grooves. Anyway, I decided to do it now instead of later so I pulled the calipers apart again. I used the brakes to pump out the piston, then grabbed it with padded pliers and was able to extract it. I will use Dremel tool to polish and clean the grooves to make them more like new.

Reason for posting:
I noticed that the new brake fluid in the bore had tinges of black. When I cleaned the new rubber seals, black residue came off on the paper towel. Bothersome. Brand new rubber seals should not easily decompose in clean brake fluid?

Should I be concerned and not be keen on All Balls rubber seals?

View attachment 52828
UPDATE: Engineering is Amazing.

Check out the brake caliper piston bore grooves, and check out the seals. Three things I found out:
1) The seals are not o-rings, they are rectangular in cross-section.
2) The wide inner piston seal groove is sub-grooved in the middle of the channel but the seal is flat on both sides.
3) The outer piston seal groove is a flat channel, but the outer seal itself is grooved on the piston contact surface.

52830


So these things are highly engineered.

I understand this allows the seal to flex outward when brakes are pushed, but pulls back when brake lever is released, which causes the piston to retract so the brakes don't drag. I verified and observed this in action.

I saw online that a very experienced ex-racer said when the brakes dragged on their flat-trackers, he replaced the inner seal with an actual o-ring and that solved their problem. Maybe. You hear all kinds of things, but proof is in the seeing and experiencing...

So if you don't clean those piston seal channels completely, including the very narrow sub-groove, then you are not letting the brakes work to their fully engineered capacity. Right? :)
 
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