Rear Master Cylinder Question

[CadXS]

I thought I would strip down the rear master cylinder to see what condition its in and to check out the seals. I've taken off the rubber boot and the circlip and was wondering what to do next? From the parts diagram I can see that there are 2 circular washers with cut-outs and I can see these but they don't seem to move. Should they just pop out after the circlip?.

Any advice much appreciated

 

[Shaun Chandler]

once the circlip is out all that is likely holding it is rust. You can gently pry it out or grasp the end of the pistonand rotate and pull. Beyond the piston is a small rubber plug then a spring.

Shaun

 

[drewpy]

give a Yank!! (pun intended)

 

[CadXS]

Thanks for the help, it was just rust and I just needed to be a bit more industrial with the washer. All in pieces now and the bore looks in good condition and the seals seem good. Given the cost and difficulty in finding re-furb kits I think a good clean and rebuild and call in done is in order.

 

[Shaun Chandler]

ya you probably found the same kit I did for the sr500 a hundred bucks is stupid. If your seals are good it may be your best bet. I have no way to tell you if this is true but I've read some posts online while looking for a kit that said the wheel cylinder kit for a 91 dodge shadow uses the same seal. May be worth looking into. If it doesn work please let me know I'm curious.

Shaun

 

[CadXS]

Will give it a go Shaun rebuilding it and see what happens. A part for a Dodge would probably be a difficult and expensive thing to source here in the UK. I'm gonna keep an eye out at autojumbles and see if I can pick one up cheap like Drewpy did...you never know...

 

[Shaun Chandler]

Ya true didn't look at your location before I metioned it. THe guy in the states I saw said it was a 5 dollar part but ya for you might not be cost effective. Ya I wish I could find the 10 dollar kit he found aswell let me know if you find one. Otherwise I'm going to possibly have to machine my own piston.

Shaun

 

[Heath Mallory]

I'm new to this group and I'm also a new owner of a 79 XS400F. While I've had quite a bit of experience working with and rebuilding 70s era metric bikes, I've never owned a Yamaha before.
I've got a pretty basic brake question. The rear master cylinder on my XS seems to be in pretty good overall condition. I disassembled it and inspected all of the parts. Things seem to be ok. It seems like it might even work without any major rebuild efforts. Here's my question... I reassembled the master cylinder and while it was still off the bike, put some brake fluid in the reservoir and began to pump the piston. The piston moves freely and returns to it's original position nicely after being pressed. It feels like it has a good tight seal, but still moves nicely. As I pump this piston with fluid in the reservoir. should I see brake fluid come out of the hole that connects to the brake line??? No matter how hard or fast I pump the piston, nothing comes out of the brake line hole.
When I had the unit disassembled, I blew it all out with compressed air and all the openings and pathways appear to be clear. Additionally, when I pump the piston, I can hear air moving, just no fluid.
Will it work properly when everything is connected and it's on the bike? I really think everything with the master cylinder is free and clear and working. It just seems like fluid does not want to flow out the brake line opening. Help!
One last thing, the rear caliper is being rebuilt, so I can't simply put it all together and try it.
Thank you for any help anyone can provide!