Author Topic: 1976 master cylinder reservoir seal  (Read 2712 times)

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Offline uglyrabbit

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1976 master cylinder reservoir seal
« on: June 28, 2016, 06:40:21 PM »
I am trying to rebuild my front master cylinder but the seal that goes under the reservoir has expanded to the point that I can no longer reinstall it. The Yamaha parts page for the master cylinder does not show it.

Offline guylr

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Re: 1976 master cylinder reservoir seal
« Reply #1 on: June 28, 2016, 08:21:20 PM »
I don't see it on any of the catalogs either. You are talking about the o-ring that goes under the nylon reservoir? Is it a standard o-ring or a square edged seal? Did you happen to soak it in a solvent that made it swell up? Sometimes washing with detergent and setting the seal out in the sun will shrink them back down again. I think the reservoir was never meant to be disassembled. If you can get the o-ring to shrink a bit, try lightly coating it with silicone grease and press the reservoir back on.

It's could be a standard size metric o-ring. I'll try to find the dimensions.

Guy
« Last Edit: June 28, 2016, 08:35:10 PM by guylr »
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"

Offline uglyrabbit

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Re: 1976 master cylinder reservoir seal
« Reply #2 on: June 29, 2016, 01:03:21 AM »
It is a standard o ring. I was just hoping someone knew the size.

Offline uglyrabbit

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Re: 1976 master cylinder reservoir seal
« Reply #3 on: June 29, 2016, 03:07:50 AM »
It is the o-ring under the nylon reservoir. It was leaking and damaged the paint, so I disassembled the master cylinder and repainted it. I want it replaced to stop it from seeping.

Offline dankeller

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Re: 1976 master cylinder reservoir seal
« Reply #4 on: June 29, 2016, 02:47:57 PM »
Uglyrabbit, I don't know the answer to your question, but I was curious how you separated the nylon reservoir from the base.

Thanks.

Offline uglyrabbit

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Re: 1976 master cylinder reservoir seal
« Reply #5 on: June 29, 2016, 02:54:19 PM »
Take the 4 screws off of the cover, remove the cover and the rubber seal.
Empty the brake fluid.
I the bottom of the reservoir are two screws, take those out.
Then I used a putty knife to get between the reservoir and the master cylinder and slowly workaround the base until I could get a plastic wedge underneath.
It should pop off after that

Offline guylr

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Re: 1976 master cylinder reservoir seal
« Reply #6 on: June 29, 2016, 03:04:33 PM »
Rabbit, if you'll measure the diameter of the flange on the reservoir and the thickness on the o-ring I'll see if there's a match in Yamaha's stock.

Guy
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"

Offline uglyrabbit

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Re: 1976 master cylinder reservoir seal
« Reply #7 on: June 29, 2016, 04:38:50 PM »
Guy, thank you for being so helpful. I'll get you those measurements ASAP
Chris

Offline uglyrabbit

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Re: 1976 master cylinder reservoir seal
« Reply #8 on: June 29, 2016, 05:57:10 PM »
The reservoir base measures 44mm and the thickness of the o-ring is 2.78mm I'm going to assume it is a 3mm X 43mm o-ring. Not sure if that is a common metric size

Offline guylr

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Re: 1976 master cylinder reservoir seal
« Reply #9 on: June 29, 2016, 10:51:08 PM »
I'll check on it in the morning and let you know.

Guy
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"

Offline guylr

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Re: 1976 master cylinder reservoir seal
« Reply #10 on: June 30, 2016, 06:22:43 PM »
Sorry, I'm not coming up with anything Yamaha sells in the States that will match that size. I'd try the silicone grease on the o-ring.

Guy
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"

Offline uglyrabbit

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Re: 1976 master cylinder reservoir seal
« Reply #11 on: June 30, 2016, 06:29:32 PM »
Guy, thanks for looking. O-ring is toast. I'll try to find a replacement and let you know how I make out.
Chris

Offline uglyrabbit

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Re: 1976 master cylinder reservoir seal
« Reply #12 on: June 30, 2016, 07:02:10 PM »
http://www.yamahatriples.com/index.php/how_tos/front-master-cylinder/
Just found this. I'm gonna see if I can find an oring with these dimensions.

Offline guylr

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Re: 1976 master cylinder reservoir seal
« Reply #13 on: June 30, 2016, 08:11:48 PM »
Good catch. Nothing in Yamaha stock that size.

Guy
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"