Checking a motorcycle's master cylinder can uncover signs of damage during motorcycle brake maintenance; learn how to check it with this free video on motorcycle brake repair.
Master cylinder from the dirt bike or the street bike that we've been working on. We know that this is bad, there's a few holes in it. Rips and tears and whatnot. So, we know that this needs to be replaced, first off. I'm going to back this nut out so we have easier access to the rubber seals. These rubber seals are bad, so don't have a problem with using a little sharp utensil or something to make sure that these come out okay. Like I said, they will be replaced. Once that is depressed and out of there, make sure it's out of your way. Inside here, you can see there's a snap ring. Now, this is an internal snap ring, so to get this out you are going to have to pinch it and close the diameter. Use a pair of snap ring pliers, get inside of there, depress it and as you can see, it comes apart fairly simple once that's done. Now, this is the main part of your plunger system with washers. There's the snap ring we undid. Now, in here is your piston set. And this is what mainly we are going to be replacing. So, you can see there is the main plunger set of your master cylinder. Your spring that's attached this will give you your depression. So, as you can see here, we have some foreign objects on the plunger face itself. That will also tell you that the seal was bad, it was letting foreign objects, as you can see here, into the braking system. So, this is why it would be important that we flush and bleed the system once we get everything rebuilt and put back together. These two are your seals that would keep, this seal will keep it from leaking out onto the brake pedal; this seal is your pressure seal. This seal is the one that holds the pressure to the brake system while the brake pedal is applied. These just come out like I said, don't have a problem getting them out with a sharp utensil or a knife or something. You will be replacing these seals, so you will need to exercise caution when putting them back in. But, taking them out, not a problem. Once that's done, we'll go ahead and clean all these parts up, rebuild the master cylinder, put it all back together.