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**sidecarKev** · 12-23-2003, 11:58 AM

Hi Pete,
I just got through cleaning up all the calipers and both the master cylinders on my 79. You are probably better off tearing all of them apart and doing the same. More than likely there is 20 year old crud built up in everything.

You can wait for your CD or you could take a bunch of digital photos to help you get it back together. I could also send you a diagram and info from the CD if you are impatient.

Take all the calipers of and remove the hoses.
Disassemble the calipers, compressed air works good to get pistons out. Be very careful doing this though, make sure nothing can be pinched between the piston and pad holder. Clean everything. Compressed air also works good here. Blow it through all the passages. Reassemble. Hopefully nothing is worn or damaged, no new parts may be necessary.

Remove the master cylinders, usually lots of stuff built up in these. Disassemble these. Somehow you have to get those screws out. Dremel maybe? Drill? Dont forget to remove the resevoirs from the master cylinders also. Remove the snap rings from around the plungers and remove the plunger and sping. Remember how it goes back together. Clean up all the crud. Reassemble.

Now you can put the calipers and cylinders back on the bike. Use new crush washers at all the hose connections. You can buy them at most dealers.

Fill up the resevoirs and bleed the system.

This usually helps out the brakes on most any bike. It just takes a little time. Don't be afraid to give it a try, if you run into trouble I or someone else can help you out. I didn't go into detail and may have forgotten something, but it will get you started.

If you just want to get the piston back in try a C-clamp.

Kevin

**kkrazyt85** · 12-23-2003, 12:46 PM

Take ur time

Be careful not to force the piston back in cocked...make sure it is going in straight

**piratepete** · 12-23-2003, 12:56 PM

Thanks for the info. This forum is amazing, people out to help each other. I really appreciate all the advice and info.

First I will try to push it back manually, but how much force is required?

It seems to be very hard to push back in.

If nothing else does it, then I will try to disassemble it and clean it out properly.

For the rear caliper, do I need to remove the rear wheel off the bike chassis before being able to remove the caliper?

/Peter

**sidecarKev** · 12-23-2003, 01:04 PM

>>>First I will try to push it back manually, but how much force is required? It seems to be very hard to push back in.

It shouldn't take to much force if you are using a c-clamp. Like kkrazyt85 said, make sure its going in straight.

>>>If nothing else does it, then I will try to disassemble it and clean it out properly.

I really recommend taking them apart, you wouldn't believe what kind of crap might be in there.

>>>For the rear caliper, do I need to remove the rear wheel off the bike chassis before being able to remove the caliper?

I think so. I did. But I also removed every part from the bike. The rear axle passes through the caliper holder and I don't think that you can remove the caliper from its holder while still on the brake disk. You can remove the rear master cylinder easily though.

Kevin
http://webpages.charter.net/kbhahn/sidecar1.html

**Ken Talbot** · 12-23-2003, 01:16 PM

The rear caliper, as well as the front ones, can be removed without removing the wheels and axles.

However, the state of the brakes indicates that a brake job is going to be just your first task. You will also want to remove the rear wheel to repack the splines and check the bearings. You will want to remove the front wheel to rapack the speedo drive and check those bearings. You may want to disassemble the triple tree to repack the steering head bearings. Oh, and did I mention crankcase, middle drive, and final drive fluids? Then you'll be ready for having a go at the carbs!

You haven't just got yourelf a new bike, you've just picked up a new hobby (or would that be bad habit?)

A little patience will go a long way, and the final product is sure to be very rewarding. When you get stuck, just come back to the list and somebody will get you on your way again....

**pgg** · 12-23-2003, 01:25 PM

Sidecarkev - checked out your webpage - sure is a classy restoration job you're doing there. Good luck.

**sidecarKev** · 12-23-2003, 01:30 PM

Thanks pgg, I don't know if I'd call it a resto though. I just want to make it a decent daily rider. I haven't updated my page in the last week or two. Its pretty much back together now. All that is left is a carb rebuild, seat re-cover, re-paint, and a few odds and ends. Then I get to get back to the sidecar. That needs some attention.

Kevin

**ratbyk** · 12-23-2003, 01:51 PM

Newby

Peter, you mentioned hydraulic oil several times in your inquiry.
1. The brakes on the XS/XJ use DOT 3 brake fluid. DO NOT! use hydraulic oil.

2. The front master cylinder cover with the messed up screws. A trick that I have used was a small sharp center punch. Starting near the outside edge of the screw tap down with the punch to get an indent into the screw head for the punch to get a purchase. Then start angling the punch over so that as you tap on it you loosen the screw. Don't get carried away with too much brute force. Patiently tap not HAMMER. If you have or can borrow an impact screw driver that would be even better.

3. Pushing the caliper piston back in. Suggest that you put a small amount of brake fluid around the piston where it enters it's bore. This will act as a lubricant; (don't use motor oil-use brake fluid). The brake fluid will also lub up the caliper seals and help prevent them from being torn up. Then put one of the old brake pads back in place against the piston. Then use a large C-clamp to push on the piston to try and get it back into it's bore. If you do not have a C-clamp a very large pair of channel lock-pliers may work.

4. Rear brake fluid level in the rear master cylinder is approximately 3/4" from the rubber seal below the top cover. You can clean up the rust on the rubber deal using rubbing alcohol. Do not use any petroleum based oil on any rubber parts. It destroys them by making them swell up and going soft. On some Master cylinders there is a sight glass along the side of the reservoir showing a high and low level.

Be extra careful of all painted surfaces with brake fluid. It loves to eat paint.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

**tctenng** · 12-23-2003, 02:07 PM

I would also suggest you check your hoses carefully. Is the brake fluid dark?? I went through an entire rebuild only to find my hoses were deteriorating from withinh. The factory actually recommends replacing the every 4 years.

Gregg

**Jerry** · 12-23-2003, 02:20 PM

A few more things to try.

Yes, the brakes don't use any engine or electrical power *except* there is a float in the rear brake master cylinder. If the fluid level drops below a certain point the floats turn on an indicator warning light in the instrument pod. Not sure if the front has the same float unit.

To remove the front MC cover if the screws are trashed...couple options. First, you could try getting one of the $20.00 kits from Sears called a "Damaged Screw Remover". These bits bite into what is left of the screw and you twist it out. The other approach is a bit more drastic. I took a Dremel tool and cut-off wheel and slotted the screw heads. This will mess up the cover; I bought a new one plus the two screws from Yamaha. New cover does not look like the original.

Pushing the pistons back into place....

If the piston is not all the way out, I've used this stunt. Take a piece of 1/2 inch threaded rod. Put it though the large hole in the outside of the caliper. On the back side (where the pads go) I put on a large asher and nut. Thread the nut up the rod. When it and the washer and nut hits the insode of the caliper it will force the piston back into the bore. Do not force! 6-10 lb-ft or torque should do it, which is low to moderate resistance to thurning the nut with an open-end wrench.

Rear and left-front brakes are tied together through a proportioning valve on the rear MC. When you bleed the system, bleed the front first as it it best to work on the longest line.

Fluid level in rear MC...mine is alomost impossible to dee. There is a brass plug on the side of the MC. I pull this off and fill the fluid to the bottom of the threaqds in this hole. Brakes work OK, warning light never comes on.

A thought...since it looks like you will be redoing much of the brake system, consider putting on new hoses. Years of use takes its toll on the inside of the brake lines, and it is not uncommon for crud to break loose once you start riding and causing problems in the master cylinders by plugging up the pressure relive ports.

**sidecarKev** · 12-23-2003, 02:33 PM

I guess I just realized you were working on an XJ, oops.

Kevin

**piratepete** · 12-24-2003, 02:19 PM

Thanks all for the info.

I managed to push the piston back in place, but I think I may have screwed up. I removed the caliper assembly off the bike (removed the barke line) and with a c-clamp I was able to push the piston back in. However it took some force to push it back and I think that it may have not gone in straight, did I damage anything?

I also see from the yamaha parts (www.yamahaparts.com and bikebandit.com) that there are 2 o-rings in the piston assembly. Was wondering, are these o-rings inside the piston assembly, that is, not visible to the eye?

How does the brake system work. Pressing the front brake lever forces the brake oil down to the caliper assembly building up pressure enough to move the piston, extending the piston and hence applying the barke pads on the rotor (or something to the effect, correct). But when you release the brake lever, how does the piston retract. I am worried that the way I forced the piston back in, it maybe stuck.

Should I try to pop the piston out of the assembly and clean it properly and re-assemble it, but first thing, how do I pop-it out and second, is t easy to reassemble (remember who you are talking to, never done this before).

The brake system maybe just one of my many problems to come. As Ken mentioned earlier, I simply didn't just get a new bike, but also a new hobby.

But to jump in blindly like this will be a big challenge for me.

/Peter

**TopCatGr58** · 12-24-2003, 10:50 PM

Brake Pistons and such

Hey there Pete,

The piston is a very snug fit, and pushing against the fluid and the rubber 0-ring seal, it will move very slowly/stiffly!! There are 2 0-rings, but only 1 for each piston, that's why they give you 2! It's not hard to get the piston back out, just reconnect the brake line and use the brake lever to pump the piston back out. There may be plenty of crud inside the caliper housing behind the piston, so it probably wouldn't hurt to go ahead and disassemble it anyways to get it cleaned up.

The piston is steel, and with water condensation inside the caliper housing, water settles to the bottom, you can get pitting of the piston from the water rusting. These pits can be sanded/grinded moderately smooth as long as they don't extend up to the slot that the O-ring seal fits into. The rubber O-ring is what makes the seal with the caliper piston chamber, not the sides of the piston!! Also, the aluminum housing doesn't rust, so you can use some brake cleaner spray to wash out the housing, and a dull flat edge to scrape out any gunk, then some emory cloth to finish it up! I had some mild corrosion around the groove in the piston, used a light wire brush to scrub/remove it from the groove.

After all parts are cleaned and dry, you can replace the O-ring, or apply a new one, coating it with brake fluid to ensure a good seal with the housing, and also put some on the inside of the caliper piston chamber as well! Then it should slide back together fairly easily, then just reattach the dust cover and metal c-ring and your good to go. The piston retracts ever so slightly when the brake pressure is released so that it doesn't keep grabbing the rotor, but if the spooge hole is gunked up in the Master Cylinder, then the brake fluid(NOT OIL) can't return and that's what keeps the pressure ON and can cause the brakes to seize/freeze/lock up!

Then just reattach the hoses, and bleed the system and that should be it! Learning as you go is sometimes the only way to do it!!
T.C.

**Jerry** · 12-25-2003, 10:39 AM

Just to claify T.C.'s note....

The "O" ring on the piston allows the piston to move forward when brake pessure is applied, then, due to the elastic nature of the ring, it retracts the piston back to its starting point when pressure is released. Movement is very limited, but enough. Most of the time the piston does not 'slide' in the bore. Every now and then the piston goes a bit past the flex limit of the ring, and moves (due to brake pressure) farther out in the bore. From this new position the flexing cycle starts again.

Overhauling the caliper is ususally a case of removing the piston, replacing the 'O' ring, cleaning the bore, and putting the piston and 'O' ring back in place. The dust cover helps keep dirt/moisture from working its way in and around the piston so it can move (either forward or back) freely.

The piston itself can rust, and if you live where salt is used on the roads, the aluminum bore can corrode. If that is the case, you will need to get new pistons or replacement calipers. Due to the unique mounting dimensions, only an XJ caliper will fit an XJ, at least in front though I think the rear is also XJ specific.

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