Started on the 750 Seca brakes

Now I know why I couldn't bleed them to save my life and also why they squeaked so damned much.

I took apart the master cylinder. The piston is corroded, the tiny little hole in the side passage is totally clogged. Poked it clear with a guitar string and now the cylinder body is soaking in some hot water and CLR. The body is aluminum, so I know the rust is just stuck on there. It looks like the main piston seal was leaking, so the lever is rusty.

Gack.

I have a rebuild kit, which comes with new spring, seals, and piston. Should take care of it, once I clean it off.

Calipers will be next.

 

Calipers are fun :wink: I did both of mine a little while back, new seals, cleaning gunk around channels, etc. Makes the bike a lot easier to push now(not to mention stop).

My two cents, you'll see a lot of bleeding advice, now the Seca has that weird master cylinder not on the bars, right? I don't know about that thing, but for my bike, the best way to bleed them is just pump and pump the brakes until you start getting some resistance, bleeding traditionally at the bleed valves, then bungee cord the brake handle back and leave it for a day. Usually the leftover air that didn't come out the bleed valves during pumping will bubble up to the MC.

Oh, and for getting the piston out of the caliper, I don't have advice, more of an anecdote. I did use Polock's "water and blowtorch" method. I tried to get video, but a watched pot never boils and all that. It was terrifying. Had the caliper in the vice, piston aimed at a box with a deflated air mattress as a backstop, me leaning around garage door with torch. Just as I'm about to give up...POP! One piston embedded in an old air mattress box, LOL. Turned out it was missing the outer "dust" seal, unless it flew off in the process.

 

I have an xj750r seca an I am having the same problem, I am no mechanic and can't find a manual that will show me how to use the rebuild kit, so I was just going to replace my MC (which is behind the headlight) with a handlebar version. What's your thoughts on this.

 

The rebuild kit was $12. The new MC is $50, or so. In my book $12 wins.

There is not much to it, really. If you can remove the MC, you can do it.

Here is a 10-step program for you:

1. Take off the MC
2. Unscrew the 10mm bolt holding the reservoir and carefully pull it off
3. Unscrew the bolt holding the lever and take out the lever.
4. Pull off the rubber boot

At this point you should have the bare MC and you should be able to see the bottom of the piston. If it's anything like mine, it will be crusty. Get a stiff brush and clean it under some hot water. You will see the snap ring.

5. Put the MC in a vise, or get a friend to hold it.
6. Take a Philips screwdriver and depress the piston
7. remove snap ring. You can use snap ring pliers, or a small screwdriver or punch to pull one end out of the groove and then carefully work it around until ring is free.
8. Carefully let go - the piston should come right out.
9. Take out the spring under the piston. Note how it all goes together. There are only four things in the MC - spring, buffer, piston and snap ring.
10. CAREFULLY pry the rubber grommet that holds the bottle to the cylinder - this is NOT included in the rebuild kit and you don't want to mess it up.

You should have an absolutely bare MC with some crud inside. Wash it out. I put it into a solution of CLR (the stuff they clean showerheads with) overnight and it cleaned up the rust. I also de-rusted the lever same way.

If you look in the hole where the reservoir grommet sits, there are two holes, a smaller and a bigger one. Make sure both are clean. I used a guitar string to clean the small one, I didn't have anything else that fit.

One thing to note - the kit includes a new seal that goes on the piston. When you put it on make sure the lip is towards the flat end (the one with no hole). Also, make sure the part that is under the lip isn't curled. You can carefully straighten it with a small screwdriver. Use clean brake fluid for lubricant.

 

The fun continues with the calipers.

The left and right side pads were worn differently. Turned out one caliper was stuck and the other was leaking.

I got them apart and then used the steam method to pop the pistons. That prompted my wife to ask just what the heck I was doing in the basement, the whole house heard the pops.

One of the caliper pins is in good shape, just worn finish. The other one is badly pitted. Seems the little rubber bellows ripped and allowed water to collect in the pin channel. I'm guessing it's time for a new one.

I will also be replacing the hoses since I have it all apart anyway.

 

Got my parts from Chacal, started to put calipers back together.

That's when I found one piston was kinda pitted. Not bad, but enough to cause me concern. Also, I didn't lube theother one enough and got is stuck. When I tried to pull it out I marred it pretty bad.

Lesson here is that piston metal is softer than you think.

Ordered some stainless pistons, we'll see how that goes.

 

Hey, im going to have to go though my brakes since they all barely work. Where are you getting the rebuild kits from? Thanks

 

Chacal has them.

http://xjbikes.com/Forums/viewforum/f=23.html

I got mine before I figured out his stuff from here: http://www.yamahapartshouse.com/home.aspx

Keep in mind, they take forever to ship.

 

thanks, but i am not seeing anything near $12. do you have a part number? which one was the slow shipper?

 

You're right, nothing cheap there.

I think I am forgetting something. I'm going to look for the receipt to make sure what I got where.

 

The 750 Seca calipers are virtually identical to the 550 calipers, so I'm speaking from experience.

REPLACE BOTH "sliding pins." The new ones are a better piece.

Chacal has new caliper pin boots, finally. They're not in his catalog, AFAIK.

Be sure to pay close attention to the re-installation of the "shim" plates that protect the holding block from the caliper.

Re-install the anti-rattle springs (the ones above the pads) BEFORE reinstalling the pistons or you might not be able to get them in.

Be sure you get the channel seals RELIGIOUSLY, dentally clean (without scratching them all to heck.) My tools of choice are bamboo barbecue skewers, cut and sharpened to shape, and a Dremel with both nylon and brass wire brushes. A "kiss" with a lit propane torch will turn the most stubborn crud to easily displaceable crumbles.

Let me know if you hit any snags. As far as the anti-dive I'm useless; my Secas aren't so blessed.

 

I used air pressure carefully applied through the brake line hole in the caliper body to dislodge the pistons. Used a bucket half full of dirty rags to catch the piston when it blew out. Very exciting, no fire required, and no damage to the metal parts!

I second the comments about a fanatical attention to getting all of the old brake fluid crud out of the entire system, top and bottom. You don't want a piece of that stuff migrating around your brake system and clogging an orifice at the wrong moment. I had an '88 CBR Hurricane with a hydraulic clutch that stopped working 200 miles from home. Turned out that a chunk of "crud" had fouled the tiny return orifice in the master cylinder and left the clutch line pressurized and the clutch disengaged. Boy, that was a fun afternoon!