ATV Front Brake Caliper Rebuild — TRX400EX |

Hi, John Talley here with Today
we’re going to be working on our 2007 Honda TRX400EX, specifically the brake calipers.
What we’re looking at is this front right one has developed a leak and it’s not coming
from the hose so that tells me it’s probably the seals on the inside. So what we’re gonna
do is remove the caliper, pull it apart, take a look at the bore and the seals and the piston
to see if we can rebuild this one with a new set of seals or if the entire thing needs
to be replaced. So let’s get started. Ok, step number one is to go ahead and drain the
system of all the brake fluid that’s in there, which I’ve already done. Fairly simple procedure;
get your length of hose, put it on the bleeder valve, open up the valve, and just start pumping
away. We’re just trying to get all the fluid out of it. Makes it a lot easier when you’re
ready to pull it apart. Otherwise, everything gets slippery and it’s not a lot of fun to
deal with. Alright, step number one, or two as it is, is to go ahead and remove the caps
that cover up the pins that the brake pads ride on inside the caliper. Under the caps
are going to be a couple of 5mm allens, and the reason I’m doing it out here is the carrier
holds the caliper in place instead of trying to do this on the teardown bench, which can
be a littlet awkward. You don’t want to pull the pins all the way out. Just go to the edge
of the threads, but leave them in there. Next you want to pull this little dust cover for
the slider pin. And it is a 6mm allen. Same thing, you just want to back it out but don’t
remove it all the way. About right there. Next, we want to go ahead and remove the output
hose which runs up to our master cylinder with a 12mm wrench. That’s actually a banjo
bolt. You want to be careful not to lose the two crush washers that are here and here.
Alright, last but not least, we want to remove the two 12mm bolts that attach the bracket
to the hub. And once we get those two out, we can take it over to our teardown bench
and I’ll show you how to remove the piston and we’ll take a look at the bore and the
seals to see if it can be rebuilt or replaced. A couple more turns…
and then off she comes. So let’s head over
to the teardown bench. Alright, now that we’ve got it off the machine, here’s what I was
talking about:that slider pin was right here and now we’ve got it disconnected so all we
need to do is rotate the bracket up and then just slide it out. Alright, our other pins
are loose so we can push down and remove them. Now we can remove the brake pads. And that
exposes our piston inside the caliper. To remove that, what we’re going to do is take
a shop towel and just lay it down in the cavity, like that. Get a little bit of compressed
air, just cups your hands over it. Pow! Doesn’t take much pressure; I didn’t put a whole lot
on that. But that will pop the piston out. And now we need to carefully bring it up because
there isn’t a lot of clearance there. Alright, once it pops out, go ahead and remove your
shop towel and then just wiggle it the rest of the way out. Just like that. Alright, what
you’re going to see inside is an outer dust seal, which we’re going to remove, and then
the inner seal, which holds back all that hydraulic fluid and pressure. Alright, from
here we’re going to go ahead and clean it out, dry it off. Alright, we have the caliper
cleaned out, everything’s looking good, I don’t see any pits in there, so I think we’re
clear to go ahead and replace the seals. Here are the two seals that we’re going to need,
and this is going to be the part number that you’re going to need to contact us about at Fairly simple to do, we’re just going in reverse of what I did earlier.
Want to go ahead and put in the actual caliper seal first, make sure it goes in flush. Don’t
want it to be bound up or rotated in there. That looks good. Next, we just want to get
in the dust seal. Of course it goes to the outside. Get it in the groove and work it
around, like so. Now they’re both in place. Alright, now with our piston seal and our
dust seal in place, we just need to coat both of those down with some brake fluid. Doesn’t
take a lot. Then go ahead and coat down our piston. And then we need to slide the piston
in place. With brand new seals you’re going to have to put a fair amount of pressure to
get it to pop in. There ya go. Alright, from here we want to go ahead and put on our bracket,
and what you want to make note of is this little washer is actually concave, so it’s
going this direction. So we want that facing toward the bracket. Be careful to not damage
your upper seal. Alright, at this point you want to just get it a little over hand tight
and we’ll do the final torque once it’s on the machine. Just enough to hold it together.
From here, we want to go ahead and get our pads in place. Make sure your shim is on.
Go ahead and put your pins through. Keep in mind there’s a spring down there so you’re
going to have to push down on them to get it to go through. Once again, you don’t have
to get them but hand tight. Because, like I said, we’re going to do the final torque
with it on the machine. The machine does a lot better job of holding it than I do out
here on the teardown bench. Spread open the pads, and now she’s ready to go. So, let’s
head over to the machine. Alright, let’s get our caliper mounted back to the machine. You
want to make sure that you have your brake pads spread apart so they’ll clear over the
rotor. Just slider her into place, then you just have your two 12mm bolts that mount the
carrier to the plate. It can be a little tricky to get them lined up, especially that first
one. Then get that one in the bottom. Alright, it’s time to get our hose back on. Remember
to have your crush washers in there, one at the bottom and one at the top. Like so. Once
again, not too tight. It’s important now to go back and get all your pins tightened down,
because remember they were just hand-tight before. And that slider. Get your dust cap
back in place, that way you’ll keep all the dirt and water out of that pin. Then replace
our caps. Now with everything snug down, all that’s left is just to bleed the brakes. Pretty
simple procedure; fill up your reservoir; go through the process of opening and closing
your bleeder valve, and be sure you get ALL the air out of it, and then do the other side
as well. If you have any air it’s going to be spongy and they’re not going to respond
the way they should, so be sure you get all the air out of the system. Well, that’s it
for this video. If you have any questions or comments just leave them below and I’ll
do my best to answer them. And if you need any of these products or parts, come see us
at Thank you!

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8 thoughts on “ATV Front Brake Caliper Rebuild — TRX400EX |

  1. I'm working on a '86 trx250r. From what I can recall, my back brake has 1 piston like this, it works fine. My front brakes need rebuilding. The front calipers have 2 pistons. Last year, they used to clamp the disk, but not let go, so I didn't use. Now, they were stuck. I got them to move, but they won't grasp the disk hard enough to stop. Being over 30 years old, they probably need new seals. What is the best way to remove 2 pistons? Put one back in a little and hold with C clamp while pushing the other out? Thanks for the video.

  2. I have a 2001 Trx300ex. The front right brake piston won’t retract after I let go of the handle. It just keeps on adding more pressure towards the rotor. It’s a new caliper, What could it be?

  3. Great video awesome information it's really detailed I definitely appreciate that it helps for the guys that don't do it everyday thanks enjoy your day

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