Front brake caliper rebuild

[US82XS]

I had no response to the question posed in this thread: http://www.xs400.com/forum/showthread.php?t=6942 so here it goes.

I removed and disassembled my front, single rotor and piston brake caliper to assess the brake fluid leaking problem. Sure enough, there are two piston seals, square rings, one inner that is larger in the thickness of the ring, and the slimmer outer one - which was worn to pieces - and is probably 3.5mm thick and 40mm ID.

A massive caliper cleanout ensued. I do not believe that anyone sells a usable rebuild kit for this caliper. OEM part numbers for these brake parts differ from those of the comparable 650.

I was thinking that some of the seals from this kit must work: http://www.mikesxs.net/product/29-0019.html but my caliper assembly looks most like the XJ650RJ's RH one based on the parts diagram.

Is there anyone out there who can give me some guidance here? The front brake is too important to mickey mouse so I really want to get this right. Thanks in advance.

 

[XSLeo]

Just looked at te parts fiche at www.boats.net It does look like the calipers off the 82 650 seca I have setting out back. They show as having a kit that is the piston and the two rubber seals. item # 4X8-W0057-00-00 $56.12 per.
They don't list the rubber parts seperate.
The inner square shaped one is the actual seal. The outer is a dust cover.
They also list the rubber parts the caliper slide on.
The Mike's kit you link is for the old style two piston caliper. I think those are 42 mm pistons. Not sure.
The parts kit #29-0016 may be closer. Thats for a 38 mm piston. The later single piston caliper.
What diameter is your piston?
www.yamaha-motor.com/sport Will get you close to the Yamaha parts site.
On there it lists it the same way.
That price for a seal and piston kit that is factory stuff isn't too far off. The seal kit and piston from Mike's is close to $50 and they are not factory stuff. For about the same price you get higher quality parts. After all they have worked for 30 years, so if the new ones last 30 years, that only $.20 a year.
With some shopping around you might find those parts cheaper.
Leo
Leo

 

[XSLeo]

Just a quick search on Ebay, Item # 270893342643 Is a rebuild kit for the XJ650. In the parts fiche at boats.net the XJ650 and the 82 XS400 use the same brakes. So that kit at $18.52 should fit your bike. Oh free shipping too.
Leo

 

[US82XS]

Thanks, Leo. The caliper has a single 38mm piston and so MikesXS 29-0016 probably would have had one useful seal. That e-bay kit did the trick, though, and front braking is much more effective now without all that leaking brake fluid. It was a real pain to get fluid back into the system but after nearly a liter of fluid cycled through, the pressure was good enough to cap the reservoir. Drum brakes might be considered obsolete but I like the simplicity of those against these disks...

 

[XSLeo]

Sometimes bleeding can be tough. But once working, they are simpler to maintain, no adjustment needed, disc self adjust. Just replace the fuid every couple years and pads as needed and they stay working much better than a drum ever will.
Leo