MC reservoir sight glass leak

[Skinner]

Firstly, I must apologize for using "JB Weld" as a generic term. The product I used is Permatex Cold Weld, which is a bonding and filling product. I've always called it JB Weld because it's less of a mouthful than Permatex Cold Weld. Not sure if that makes a difference in this discussion, but there it is.

The product is an adhesive and filler that bonds to many metals, aluminum included, and resists automotive, shop and cleaning fluids.

I'm well aware that we are discussing a critical safety system on the bike, and I don't take it lightly, which is why I chose this solution. I first tried the watch crystal with RTV and, while it looked good, I was informed on this forum that brake fluid will eat RTV. I then tried the repair with epoxy and had similar results - it didn't hold well. It's a difficult opening to work with. In the end I didn't think anything I could do with the watch crystal or a piece of Lexan would give me the confidence that it would hold. So I decided to fill the opening flush with the Permatex and call it a day.

I guess time will tell, and I'll just agree to disagree. That said, if I see any signs of degradation in the repair I'll be the first to suck it up, put my tail between my legs and report back here.

[Skinner]

That is exactly what I was thinking. No drama intended, but somewhere down the line, someone else is going to read this thread and see at least two ways of doing the job.

That's why I responded with a picture and explanation. I realized what your intentions were and wanted to clarify that I wouldn't just fill an open hole with JB Weld. My sight glass opening isn't open into the reservoir and has backing, and it has the mechanical advantage of the o-ring groove.

I know that JB is rather resistant to most chemicals, I don't know whether brake fluid affects it or not, but you certainly can NOT see through it.

And that's the disadvantage, which I am aware of. I'll be checking my brake fluid level regularly. That said, the whole reason for my initial attempt was that you could not see through the original sight glass. When I disassembled everything I realized that the sight glass was unlike most others. It led me down this path.

[Admiral Beez]

Visits to the emergency room are crazy expensive.....

My son dropped his Concours 14 at about 5 or 10 mph in Feb. That little accident was about $50,000 so far and it's not over.
https://photos.app.goo.gl/Q8mIFBCZOJkQPBcj1

I don't know how Americans get by without health insurance. Our Canadian system isn't perfect, but with my family seeing its share of accidents, babies born, knees/hips replaced and cancer fought, I'll wrap myself in red and white.

On the site glass, I assume it's fine on the inside, but that may be naive. How can I polish up the cloudy outside?

[Cipher]

There is a nice write up about sight glass replacement kicking around here or on the interwebs.
I wonder what they used. A;so wonder what the factory used.

[Cipher]

from the kits I see it seems they are a pressure fit with an o-ring

[TxGSrider]

I haven't used the Permatex Cold Weld but JB weld can be a little brittle. I don't think its affected by brake fluid, but I don't know. Would I use it to fix a broken lens... yes, but only as a temporary fix to get back on the road if I was broke down someplace, or if I needed it for a short ride. But as soon as I could I would try to find another master cylinder.

[Skinner]

I haven't used the Permatex Cold Weld but JB weld can be a little brittle. I don't think its affected by brake fluid, but I don't know. Would I use it to fix a broken lens... yes, but only as a temporary fix to get back on the road if I was broke down someplace, or if I needed it for a short ride. But as soon as I could I would try to find another master cylinder.

It's been 2 months since I completed this repair. There has been no degradation of the Permatex, no loss of brake fluid, no signs of any movement from the repair (no paint cracks, etc.) I check the brake fluid regularly and the level has not moved. So far I have no concerns about the repair.

[nejeff]

It's been 2 months since I completed this repair. There has been degradation of the Permatex, no loss of brake fluid, no signs of any movement from the repair (no paint cracks, etc.) I check the brake fluid regularly and the level has not moved. So far I have no concerns about the repair.

Your insane dude. By a new m/c please. You think the degradation of the Permatex is going to stop? You'll realize when you need to grab hard for an emergency stop and it blows out that you were wrong.

[Skinner]

Your insane dude. By a new m/c please. You think the degradation of the Permatex is going to stop? You'll realize when you need to grab hard for an emergency stop and it blows out that you were wrong.

Not worried about a blowout - there is no pressure in the reservoir.

[Skinner]

Your insane dude. By a new m/c please. You think the degradation of the Permatex is going to stop? You'll realize when you need to grab hard for an emergency stop and it blows out that you were wrong.

My apologies - my post should have said "no degradation of the Permatex" - I have since corrected it.

[Skinner]

from the kits I see it seems they are a pressure fit with an o-ring

That's what they are, and they are all 18mm, at least the ones I could find after extensive searches. The opening in my reservoir was around 21mm, and it was not just a hole through the metal - there is a backing piece (see earlier pics). The readily available site glass kits would not work for my reservoir.

The OEM sight glass was some sort of plastic with an o-ring seal that fit into a groove in the aluminum. This was covered by a metal "cap" that was press fit to hold everything in place.

[Admiral Beez]

Before you fill the void with JB, try a small piece of Plexiglass or Lexan. I have done several over the years, with no reported or observed failures.

.

I see replacement lens and o-ring kits on eBay.