This is for purposes of information only, as a discussion of what can be done by the bike owner should he decide to fix a caliper. If this is beyond your skills, pay to have a professional mechanic perform your brake repair. Use new OEM parts, and a new can of brake fluid.
Do you have a sticky brake caliper? Dread trying to pay for fixing it? Did you start to attempt a repair, and get bogged-down? I may be able to help you in your repair.
In my experience, unless the bike has been submerged in water, you can fix the brake caliper(s) yourself,just by disassembly, cleaning, and careful reassembly, and it should only cost you some brake fluid, if you have the appropriate tools on-hand. Even if you don't, you can get what you need inexpensively, and your fix will pay for itself on the first caliper you overhaul.
'Cleanliness is next-to godliness,' it's said. That goes for working on brakes. Remove any corrosion you find. Clean things thoroughly, then clean them again, before reassembly. After all, what depends on your job of repair?
The customary way to remove the pistons from our opposed-piston systems is with an air hose, or removal of the caliper, while still hooked to the brake line, and pumping the lever or pedal until the pistons come-out of their bores.
Sometimes, because of corrosion, one piston may not move, while the other does. You need to hold the moving piston stationary, while in-effect transferring hydraulic pressure to the stuck piston. Usually a C-clamp will be used to hold the moving piston stationary, (caliper removed from the rotor) and a few pumps will force-out the other piston.
Sometimes the stuck piston still won't move. The use of an air hose will sometimes force-out the stuck piston, if you remove the bleeder and use a rubber-tipped air hose to pressurize the stuck side of the caliper. Be aware that if the piston comes-out completely, you're going to have corrosive brake fluid everywhere. Use a shop rag around the entire caliper to contain any fluid.
The lever or the brake pedal didn't work to free the stuck piston? The air hose didn't work to free the stuck piston? Waaahhhh!!!
Here's what I've used in that situation. Buy a metric grease fitting, M8 X 1.25 and remove the bleeder from the caliper side which has the stuck piston. Install the grease fitting into the brake bleeder hole. You don't need to tighten it down, just get it snug.
A tip: the bolt size that holds the caliper to the fork slider or to the carrying bracket in the rear is the same size as the caliper hose fitting. When you unscrew the banjo bolt for the brake hose, you can use the mounting bolt to block-off the threaded hole. You do-not tighten the screw in the hole! Just run it in until you feel it's at the bottom, and stop. This will be enough to use air pressure or my other method to pop loose the pistons.
Now use a grease gun to fill your caliper with-grease! Yes, grease. The grease gun develops much-more pressure than your brake lever or an air hose inside the caliper. The piston will come-out. Again, be aware that when it exits the caliper bore, you will have a mess, so thoroughly cover the entire caliper with a shop rag to contain everything.
If you're careful, you can get the piston to almost remove itself. This will save the big mess if you just squeeze the grease gun lever until the piston pops-free out of the caliper. When the piston is almost out, you can remove it the last bit manually, it's that-loose. Now you have to totally disassemble the caliper halves, they're bolted together. You're the owner of a manual impact tool, yes? If you're working on your motorcycle and you don't have one, get one, now! I prefer a 3/8" drive and a 20 or 24 ox ball pein hammer. Use the impact driver to loosen the two bolts holding the caliper together. See the flat rubber washers in the corners of the opened calipers? Set them aside.
If you used the grease gun to remove a stuck piston, remove the metric grease fitting you inserted into the caliper side with the stuck piston. All grease needs to be thoroughly removed with brake cleaner aerosol.
Use brake cleaner to clean up the grease. A roll of paper towels is good and I use a plastic bag to be my wastebasket for the dirty towels, and they are removed from the building anytime I stop, to prevent spontaneous combustion of petrochemicals from starting a fire. A combustible materials receptacle is a safety item to have, along with a couple 5 lb ABC dry chem extinguishers.
You should have the pistons out of their bores. You should have the caliper halves cleaned of the grease, don't forget the passageways going from one caliper half to the other, and the bleeder passages. Use a good aerosol brake cleaner w/its red plastic wand to clean these tiny passages.
Another tool you should have is a dental pick, to remove the o-rings in the calipers. Be careful using the pick, as you can probably re-use the rubber o-rings that are the seals to the pistons, if you exercise some care in their removal.
Now just look at that corrosion in the o-ring lands (the grooves) of the caliper halves! Now you have an idea of what your dentist sees.
You have a 120 V rotary tool like a Dremel, yes? And a couple of brass round flat brushes to use in it? A good size is about 1-1/2" for the disc brushes. If you don't have a Dremel, buy one! Or, visit Harbor Freight Tools (HFT) and get their generic one, they're cheap, and buy an assortment of brass brushes, they come packaged together, various shapes and sizes. The disc brushes are best for cleaning the o-ring lands (grooves).
Get busy on using the brass brush and the Dremel, or the HFT on the piston area of the caliper halves. It seems that due to water getting into the area of the bottom of the o-ring lands, it sits in there and causes corrosion more-than the top, where water probably won't sit.
Remember that dental pick? You can use that to scrape the inside edges of the o-ring lands to get out any stubborn deposits. When you're done use the aerosol brake cleaner to thoroughly clean all residue from both caliper halves. The paper towels are good for this too. Wipe and discard, grab a fresh towel.
The o-rings probably will have white deposits on them. Use a scotchbrite pad and your aerosol brake cleaner to scrub the o-rings. Get them clean of any deposits. If they clean-up well, you may be able to re-use them. If your o-rings are damaged, replace them. Any doubts about their condition, replace them.
Remember those flat o-rings in the corners of the caliper when you split it apart? If you did the grease-gun trick, they need to be cleaned as they will have grease on them. Grease and brake fluid should never mix! Use a clean paper towel and your aerosol brake cleaner.
OK, everything's clean. Time for reassembly. Install the o-rings into their respective grooves/lands. Take a bit of clean new brake fluid and run it around the inside surfaces of the caliper hole/o-rings where the piston will sit. This is needed lubrication for the pistons and o-rings. Insert the pistons, but don't push them all the way into the caliper half. Leave maybe a 1/4 inch of the piston above the edge of the caliper body. Before you reassemble the caliper halves: the pistons should move freely with finger pressure when you grip the insides of the piston, and move it in and out.
Got both caliper sides done? Now install the two corner of the caliper, o-rings into their recesses on one of the piston halves. The other caliper half does NOT have a recess for the o-ring.
Did you use your bench grinder wire wheel to clean the large machine screw threads holding the caliper halves together? Did you use some brake cleaner to clean the threads in the caliper half which is threaded for those bolts? Snug down the bolts, and torque them appropriately, refer to the factory shop manual for the torque values of that size fastener.
Clean the brake caliper bleeders on your bench grinder wire wheel. Use the aerosol brake cleaner to clean the passageways of the bleeder nipples, and you already cleaned the caliper halves where the bleeder nipples go, earlier, yes? Remember that if you had to use the grease gun method of piston removal, that you installed a metric grease fitting in-place of one of the bleeders, and that now needs to be removed, if you didn't already, once you split the caliper halves and cleaned everything.
Don't forget to clean the brake hose banjo bolt on a wire wheel and with brake solvent aerosol. It's time to re-install your caliper. I suggest filling each side of the caliper at the bleeder nipples (remove them to fill the caliper with fluid, then re-insert the bleeder nipples, and snug them until you are ready to bleed through them) with fresh brake fluid.
I suggest you do a reverse-bleed of the VMax brake system. You can search on the forum for a post under my screen name and 'reverse-bleed.' The same technique can be done with the hydraulic clutch slave cylinder.
If you were doing the rear brake, as I was, you should be done. If you're doing the front brakes, you've done one caliper, and you have another to do.
On rare occasions, a brake hose may collapse internally, and fluid will not flow back and forth. The collapsed hose acts like a one-way valve. It holds pressure on the caliper, and you will need to crack a bleeder to release the pressure to allow the wheel to rotate again. Replacement of the brake hose(s) is the only option. do not attempt to clean them internally to return them to service.
What are you waiting for? Get to work, and enjoy proper braking. This would be a good time to install new HH-rated pads if you're doing the front calipers. If you have oil from a leaking fork downtube oil seal contaminating the brake pads, fix the fork seal(s) before replacing the brake pad(s).
Do you have a sticky brake caliper? Dread trying to pay for fixing it? Did you start to attempt a repair, and get bogged-down? I may be able to help you in your repair.
In my experience, unless the bike has been submerged in water, you can fix the brake caliper(s) yourself,just by disassembly, cleaning, and careful reassembly, and it should only cost you some brake fluid, if you have the appropriate tools on-hand. Even if you don't, you can get what you need inexpensively, and your fix will pay for itself on the first caliper you overhaul.
'Cleanliness is next-to godliness,' it's said. That goes for working on brakes. Remove any corrosion you find. Clean things thoroughly, then clean them again, before reassembly. After all, what depends on your job of repair?
The customary way to remove the pistons from our opposed-piston systems is with an air hose, or removal of the caliper, while still hooked to the brake line, and pumping the lever or pedal until the pistons come-out of their bores.
Sometimes, because of corrosion, one piston may not move, while the other does. You need to hold the moving piston stationary, while in-effect transferring hydraulic pressure to the stuck piston. Usually a C-clamp will be used to hold the moving piston stationary, (caliper removed from the rotor) and a few pumps will force-out the other piston.
Sometimes the stuck piston still won't move. The use of an air hose will sometimes force-out the stuck piston, if you remove the bleeder and use a rubber-tipped air hose to pressurize the stuck side of the caliper. Be aware that if the piston comes-out completely, you're going to have corrosive brake fluid everywhere. Use a shop rag around the entire caliper to contain any fluid.
The lever or the brake pedal didn't work to free the stuck piston? The air hose didn't work to free the stuck piston? Waaahhhh!!!
Here's what I've used in that situation. Buy a metric grease fitting, M8 X 1.25 and remove the bleeder from the caliper side which has the stuck piston. Install the grease fitting into the brake bleeder hole. You don't need to tighten it down, just get it snug.
A tip: the bolt size that holds the caliper to the fork slider or to the carrying bracket in the rear is the same size as the caliper hose fitting. When you unscrew the banjo bolt for the brake hose, you can use the mounting bolt to block-off the threaded hole. You do-not tighten the screw in the hole! Just run it in until you feel it's at the bottom, and stop. This will be enough to use air pressure or my other method to pop loose the pistons.
Now use a grease gun to fill your caliper with-grease! Yes, grease. The grease gun develops much-more pressure than your brake lever or an air hose inside the caliper. The piston will come-out. Again, be aware that when it exits the caliper bore, you will have a mess, so thoroughly cover the entire caliper with a shop rag to contain everything.
If you're careful, you can get the piston to almost remove itself. This will save the big mess if you just squeeze the grease gun lever until the piston pops-free out of the caliper. When the piston is almost out, you can remove it the last bit manually, it's that-loose. Now you have to totally disassemble the caliper halves, they're bolted together. You're the owner of a manual impact tool, yes? If you're working on your motorcycle and you don't have one, get one, now! I prefer a 3/8" drive and a 20 or 24 ox ball pein hammer. Use the impact driver to loosen the two bolts holding the caliper together. See the flat rubber washers in the corners of the opened calipers? Set them aside.
If you used the grease gun to remove a stuck piston, remove the metric grease fitting you inserted into the caliper side with the stuck piston. All grease needs to be thoroughly removed with brake cleaner aerosol.
Use brake cleaner to clean up the grease. A roll of paper towels is good and I use a plastic bag to be my wastebasket for the dirty towels, and they are removed from the building anytime I stop, to prevent spontaneous combustion of petrochemicals from starting a fire. A combustible materials receptacle is a safety item to have, along with a couple 5 lb ABC dry chem extinguishers.
You should have the pistons out of their bores. You should have the caliper halves cleaned of the grease, don't forget the passageways going from one caliper half to the other, and the bleeder passages. Use a good aerosol brake cleaner w/its red plastic wand to clean these tiny passages.
Another tool you should have is a dental pick, to remove the o-rings in the calipers. Be careful using the pick, as you can probably re-use the rubber o-rings that are the seals to the pistons, if you exercise some care in their removal.
Now just look at that corrosion in the o-ring lands (the grooves) of the caliper halves! Now you have an idea of what your dentist sees.
You have a 120 V rotary tool like a Dremel, yes? And a couple of brass round flat brushes to use in it? A good size is about 1-1/2" for the disc brushes. If you don't have a Dremel, buy one! Or, visit Harbor Freight Tools (HFT) and get their generic one, they're cheap, and buy an assortment of brass brushes, they come packaged together, various shapes and sizes. The disc brushes are best for cleaning the o-ring lands (grooves).
Get busy on using the brass brush and the Dremel, or the HFT on the piston area of the caliper halves. It seems that due to water getting into the area of the bottom of the o-ring lands, it sits in there and causes corrosion more-than the top, where water probably won't sit.
Remember that dental pick? You can use that to scrape the inside edges of the o-ring lands to get out any stubborn deposits. When you're done use the aerosol brake cleaner to thoroughly clean all residue from both caliper halves. The paper towels are good for this too. Wipe and discard, grab a fresh towel.
The o-rings probably will have white deposits on them. Use a scotchbrite pad and your aerosol brake cleaner to scrub the o-rings. Get them clean of any deposits. If they clean-up well, you may be able to re-use them. If your o-rings are damaged, replace them. Any doubts about their condition, replace them.
Remember those flat o-rings in the corners of the caliper when you split it apart? If you did the grease-gun trick, they need to be cleaned as they will have grease on them. Grease and brake fluid should never mix! Use a clean paper towel and your aerosol brake cleaner.
OK, everything's clean. Time for reassembly. Install the o-rings into their respective grooves/lands. Take a bit of clean new brake fluid and run it around the inside surfaces of the caliper hole/o-rings where the piston will sit. This is needed lubrication for the pistons and o-rings. Insert the pistons, but don't push them all the way into the caliper half. Leave maybe a 1/4 inch of the piston above the edge of the caliper body. Before you reassemble the caliper halves: the pistons should move freely with finger pressure when you grip the insides of the piston, and move it in and out.
Got both caliper sides done? Now install the two corner of the caliper, o-rings into their recesses on one of the piston halves. The other caliper half does NOT have a recess for the o-ring.
Did you use your bench grinder wire wheel to clean the large machine screw threads holding the caliper halves together? Did you use some brake cleaner to clean the threads in the caliper half which is threaded for those bolts? Snug down the bolts, and torque them appropriately, refer to the factory shop manual for the torque values of that size fastener.
Clean the brake caliper bleeders on your bench grinder wire wheel. Use the aerosol brake cleaner to clean the passageways of the bleeder nipples, and you already cleaned the caliper halves where the bleeder nipples go, earlier, yes? Remember that if you had to use the grease gun method of piston removal, that you installed a metric grease fitting in-place of one of the bleeders, and that now needs to be removed, if you didn't already, once you split the caliper halves and cleaned everything.
Don't forget to clean the brake hose banjo bolt on a wire wheel and with brake solvent aerosol. It's time to re-install your caliper. I suggest filling each side of the caliper at the bleeder nipples (remove them to fill the caliper with fluid, then re-insert the bleeder nipples, and snug them until you are ready to bleed through them) with fresh brake fluid.
I suggest you do a reverse-bleed of the VMax brake system. You can search on the forum for a post under my screen name and 'reverse-bleed.' The same technique can be done with the hydraulic clutch slave cylinder.
If you were doing the rear brake, as I was, you should be done. If you're doing the front brakes, you've done one caliper, and you have another to do.
On rare occasions, a brake hose may collapse internally, and fluid will not flow back and forth. The collapsed hose acts like a one-way valve. It holds pressure on the caliper, and you will need to crack a bleeder to release the pressure to allow the wheel to rotate again. Replacement of the brake hose(s) is the only option. do not attempt to clean them internally to return them to service.
What are you waiting for? Get to work, and enjoy proper braking. This would be a good time to install new HH-rated pads if you're doing the front calipers. If you have oil from a leaking fork downtube oil seal contaminating the brake pads, fix the fork seal(s) before replacing the brake pad(s).
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