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View Full Version : Don't throw away those master cylinders - site glass fix!



Flossyb20
08-14-2014, 12:01 AM
So I'm sure a lot of us have a few master cylinders for our Rs and Xs that have the site glass rotted out or you just cant see through anymore...I did a search on here and the only recommended fix was to JB weld it, or use plexiglass. We'll here's a proper fix that only cost me $8.00 from hobby lobby.
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What you'll need:
Small flat screwdriver or pick
Modeling clay (play-doh will work as well)
Mold release (pam works too)
Ice Resin (a 2-part crystal clear acrylic resin from Hobby lobby)
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Step 1:
Remove all the old site glass residue from the master cylinder, be sure to get it all, otherwise you risk damaging the backing plate or retaining ring you'll need to make a new one.
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Step 2:
Once all is removed, push out the backing plate and retaining ring from the inside with your small screwdriver, taking care not to twist or mangle them by applying pressure around the edges. With all the old resin out, both should come out fairly easy.
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Step 3:
Now that you have the ring out, you'll notice there's an o-ring behind the plate...while not necessary, I recommend replacing this - I used an A/C o-ring myself, has held up fine for 3 years so far. This is also a good time to refinish you're master cylinder if you'd like, I used VHT epoxy in gloss-black...very nice finish.

Step 4:
Take your modeling clay (or play-doh) and get a nice level surface to work with, I used a large kitchen knife and pressed down. Once you're satisfied with you're surface, lightly apply you're mold release (or pam) if you don't, then the clay will stick to your new resin.

Step 5:
Now, gently press the retaining ring into the clay, just enough to seal the bottom. Try not to let the clay push up through the bottom
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Step 6:
It's time to mix up the Ice Resin...it comes out in a 50/50 mixture. Mix more than you'll need...if you're stingy, you may not get a great mixture. Once you've mixed the resin, very slowly pour it into the ring. Pour just enough to get a slight dome, don't worry about the bubbles, they'll work themselves out. Let it sit overnight, and voila, a new slight glass!...simply press everything back in your master cylinder and you're done.

the great gazoo
08-14-2014, 08:04 PM
Very cool, I'm definitely going to try this on a couple that I have.
Thanks for this, bro.

6speedthumper
08-14-2014, 09:10 PM
Well I know I'll be using this in the future!

Stephon_xr500
08-14-2014, 09:31 PM
I love the step by step instructions! Great post. I've been doing something similar for a few years with great results. If you don't have modeling clay handy you can use a dime just file it down until it has a small enough diameter to fit.

aldochina
08-15-2014, 02:41 PM
so you did this 3 years ago and its still holding up? has the resin yellowed at all or anything? great post

just ben
08-16-2014, 09:54 AM
I could not find ice resin at hobby lobby. The stuff I found that looks like the same stuff you have is a crystal clear epoxy

aldochina
08-16-2014, 12:38 PM
let us know how it goes Ben. More info flossy!!

muthey
08-16-2014, 12:42 PM
I could not find ice resin at hobby lobby. The stuff I found that looks like the same stuff you have is a crystal clear epoxy

here you go ben. http://shop.hobbylobby.com/products/ice-resin-singles-225268/

just ben
08-17-2014, 10:11 AM
I did one yesterday on a junk master. So far so good.

Flossyb20
08-23-2014, 12:53 AM
Sorry for not getting back, been crazy busy. The one I did 3 years ago is holding up good, a little duller than when new, but not yellow and still transparent. Ben...how did yours work out with the crystal epoxy, or were you able to find the ice resin?

nstyle73
08-23-2014, 07:35 AM
Any chance someone wants to repop one of these? My master cylinder has two rubber grommets and a bolt holding them together where the sight glass is. I if I buy a master cylinder for the sight glass, I might as well use the whole thing.

MIK6
08-23-2014, 09:13 AM
Ive got a few to repair as well..
bring the supplies on your next visit ben!! Lol

just ben
08-23-2014, 10:36 AM
I wanna get up there before the snow flies mike. We could do a few. I did it a little different, I left the metal ring in the master and cast it in place. I figured it was less work and less likely to leak.

chargercharlie
08-23-2014, 02:12 PM
If you go to the aisle where model planes are..I believe you can find it there also..its called window maker..comes in a tube also..

just ben
08-23-2014, 02:34 PM
Also called casting resin

ps2fixer
08-23-2014, 08:56 PM
Nice write up, I looked around and couldn't find anything similar to this method, closest thing I could find is to epoxy in actual glass, but I like this repair much better. I also found an ebay seller for the sight glasses, $15 seems a bit pricey though. Here is the link if someone is interested.

http://www.ebay.com/itm/sight-glass-OEM-motorcycle-master-brake-cylinder-sight-glass-replacement-/321486506189?pt=Motorcycles_Parts_Accessories&hash=item4ada16c8cd&vxp=mtr