Hi this is John Talley with Partzilla.com. Today we're working with our 2007 Honda TRX400EX.
More specifically, we're working on the front braking system. Today we're going to pull
apart and evaluate the front master cylinder because the front brakes feel a little
spongy. So that's something we need to take care of. The first step in this process is
just pulling this cap, and then I need to come around to the other side and bleed all
the fluid out of it. Now to get off this cap, you really need this particular tool. This
is an impact wrench with a phillips head driver on it. If you don't have this, I can pretty
much guarantee you're going to strip out the heads. So to get us started, let's go ahead
and pop those loose. Alright, now I am going to get these pulled out then I'm going to
shift around to the front and go ahead and bleed the system.
Alright, you saw me use this impact driver but what we need to do now is just run through the other tools that
are going to be required. A couple different sockets -- a 10 and an 8mm; two different
wrenches -- a 12 and a 10mm; then you want to have a set of pliars for the circlip and
needle nose; then a couple of picks to help work out the circlip that's going to be inside
the master cylinder. Alright, now we've got our master cylinder cap removed and what that
allows is the for the air to get behind the fluid, that way we can purge it through the
system. And it's just your regular bleeding procedure, so you want to pump it up a few
times, and then use that 8mm wrench on your bleed screw to release it. Pump it up, and
release. Pump it up, and release. Now when you have just air getting pumped through the
system, that means you're done but this is going to take me a little while so once I
get this finished, I'll come back and show you how to remove the master cylinder from
the unit. Now we've got all the fluid purged from the system, so it's time to go ahead
and remove the master cylinder from the handlebar. To get that done, what we need to do is go
ahead and remove this boot, pull that back, there's a pinch bolt on the bottom that's
a 10mm, go ahead and pop that loose. And just take it all the way off. Like I said, it's
just a pinch bolt. Now the actual pivot bolt is still threaded into the housing itself.
So that will need to come all the way up before you can get it to release. That's threaded
out. Grab the handle, and there it comes. Next there's a couple of wires that actually
activate the brake light attached here at the bottom. Go ahead and pull them both off.
It's just a contact, so polarity doesn't matter. From there, we want to take off our main output
hose. It's a banjo bolt. Remember it has two washers on it, you don't want to lose those
otherwise it's going to leak profusely. There she goes. That's that washer I was talking
about, and there are two of them, the top and the bottom. Alright, from here you have
just a couple of 8mm bolts that clamp on to the handlebar. You want to go ahead and do
the bottom one first, get it removed, and give it just a little bit of a tap so you
clear the throttle cable, to get to the other one. Once we get that, then we'l head over
to the teardown table to pull it apart and check our seals on the inside. So let's head
over to the table. Alright, so now we have the master cylinder off the machine, and we
just need to take it apart. What you're going to find inside is basically made up of three
pieces. You've the the piston with the spring, a circlip, and on the outside just a rubber
boot. So let's go ahead and get the boot removed. This can be a little tricky because that circlip
is way down in there. What you want to do is squeeze it, bring it just up inside where
it seats, then use a pic tool to go ahead and pry it out. It can be a little arduous.
Don't stick yourself with your pick tool while you're doing this. There we go! And then lift
out the piston with the spring on it. Alright from here, we want to go ahead and spray it
down with a little bit of brake cleaner. If you have compressed air, go ahead and blow
it out. Now we can take a look at the bore. Now what we're looking for inside the bore
is to make sure there's no pitting. So you just want to inspect that area all the way
down, particularly up to that edge, making sure there's no pitting anywhere around inside.
Everything looks pretty good, so now we can just get our new assembly, coat it down with
a little bit of brake fluid, doesn't take much. Just want to get the seals lubricated.
Slide it back down into the bore, grab our new circlip. The trick here is to get it just
inside the bore, and then push it down with our pick tool. You want to keep pushing until
you hear it click into position. It can be a little challenging but you'll hear that
click here in a second. There we go! That's one side. There we go! From there, we just
get our rubber boot back on and now she's ready to go back on the machine. So let's get it mounted back on. Alright,
now with our master cylinder rebuilt, installation is just the reverse of removal. What we had
were just these two 8mm bolts which connected the clamp to the handlebar. Once you pull
it back up into position, make sure that the joint where they come together is in line
with the handlebar itself. That will tell you that you've got it in the right position.
After that, you connect up these two wires for the brake light, and remember the polarity's
not important. So it doesn't matter which direction they go. After that, reconnect your
main line going down to the brake calipers. Make sure you've got the crush washers on
the inside and the outside. After that, you just put in the main pivot point for the brake
lever itself, thread it all the way through, and then cinch it up with the locknut on the
bottom. After you do that, just pull that boot to cover up everything, and at that point
we just need to bleed the system and she'll be ready to go. Alright guys, we've got our
master cylinder reassembled, and we've attached it to the machine. All we need to do now is
just refill it. I prefer using the Honda DOT4 brake fluid. You want to fill it up about
three-quarters of the way, then we're going to go through our regular tried-and-true bleeding
procedure which is this: I'm going to pump it up about three or four times, reach down
with this held in, and release the valve, and then close it. Pump it up, hold, release,
and then close. Alright this procedure is going to take me about ten minutes and once
I have a steady stream of fluid going through the hose, I'll go to the other side, bleed
the other caliper, and then that should finish the procedure. At that point, all we need
to do is reattach our reservoir cap and then we can call this procedure done. Alright,
with our bleeding procedure complete all we need to do now is just reinstall the cap.
Keep in mind there's a couple of different pieces. If you look right here, you've got
this outer plastic cover, attached to it is this rubber seal. You want to check that seal
to make sure there's no cuts or tears or anything like that, and if you do need one of these,
we have it at Partzilla.com. Alright, you want to just slide that into the reservoir,
it's non-directional so it doesn't matter which way. Then you have your cover with some
writing on it. I prefer that to be facing the rider. From that point, you just have
a couple of phillips screws to hold the cover down. Get those reinstalled, don't over tighten
it because remember it is just aluminum. And now this procedure is complete. So if you
have any other questions or comments, if you would, just leave them below and I'll respond
to them. And if you need any of the products you've seen, or the chemicals that we used,
they're available at Partzilla.com. Thanks for watching, and I'll see you next time.