In this video we’ll demonstrate how to rebuild a motorcycle or ATV master cylinder. When your brakes fade or feel spongy, it’s usually a good sign your master cylinder needs a rebuild. The seals can wear out and cause air to enter the system, therefore drastically reducing your stopping power. Rocky Mountain ATV/MC carries all the parts and tools you need to get your breaks working at their full potential, including the OE parts for your machine. We’re only going to need a few standard tools to complete this job. It’s also a good idea to have your service manual handy. So we’ll start by removing the brake lever. This one has a mount on the bottom and it also threads into the master cylinder as well. As you pull it, watch for a spring and/or pushpin, as some levers will have them. That’s going to reveal the rubber boot. So to gain easier access to that, we’re going to loosen the master cylinder clamp bolts and slide it down the handlebar. For illustration purposes, we’ve also pulled our throttle tube and housing as well to better show the rebuild process. Now using a small screwdriver, go ahead and remove that rubber boot. Doing that is going to reveal a circlip. To remove that it’s easiest just to pull the master cylinder from the bars, and then use your circlip pliers to get down in there and pull it out. Notice we’ve got our finger on the piston to make it easier to remove. With the circlip out you can pull the piston assembly and spring from the master cylinder. We just zip-tied our master cylinder to the bars to keep it from leaking all over. So as you can see, the seal is obviously bad with a few small nicks in it. If you decided to go with an OEM rebuild kit, keep in mind each kit will vary with its included parts. They will usually always come with a piston, seals and spring. But you’ll just have to refer to your machine’s OEM diagram on our website for a specific list of parts. If you go with an aftermarket rebuild kit you’ll find they rarely include a piston, but they do come with the seals, spring and a few more parts to replace. You’d just simply remove your old seals from the piston and install these new ones included with the kit. We chose to install an OEM rebuild kit, which usually comes with everything. We just need to assemble it exactly like the one we pulled out. So we’ll put a little brake fluid on there to lube it up, and then slide that first seal down into place. Make certain the seal gets installed facing the right direction and into the right place on the piston. You may need to use a small screwdriver to help get it into position, being careful not to tear or damage either seal when installing them. Once you have the first one, move on to the other seal. Now we just have to install the spring and our piston is ready to be installed. We’re going to lube up both seals again before we slide on the washer and circlip, and then install the piston back into the cylinder. Make sure there’s smooth action before installing the circlip down into its groove. It’s always a good idea to use a small screwdriver to make sure it’s seated all the way. The next step is to re-install the rubber boot. Use a small screwdriver to seat that down into place. Now we can remount the master cylinder to the handlebars, and then reinstall our brake lever. Install that top pivot bolt and tighten it down. Then install the locknut on the bottom. It’s necessary to bleed the brakes after performing any kind of maintenance to the system. So first remove the reservoir cap and rubber gasket. And some reservoirs will have a little foam piece that sits on top of the fluid. Go ahead and pull that out and we’re first going to try back bleeding. We do this by spreading the break pads to try and push any air back up to the top of the reservoir. If this doesn’t work for you, you’ll need to bleed the system conventionally and you can refer to our other videos that outline each step to do that. It’s also a good idea to replace the fluid after you’ve done any work on the brakes. Old worn-out brake fluid can contribute to brake issues including overheating and fade. So we’re going to go ahead and change this fluid and finish bleeding these brakes. When you’re done your lever should tighten right up. Once you get to that point you’re done with the rebuild. And these steps would basically be the same if you’re rebuilding the rear master cylinder. So if you have any questions about your brakes feel free to give us a call at 1-800-336-5437 or visit us online www.RockyMountainATVMC.com. Thanks for watching!