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I.T. Analyst, Alpha Geek
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157 Posts
Discussion Starter #1 (Edited)
There is no replacement part # for our brake fluid sight glasses, and the only part I can find is on eBay with about 450% markup, and the guy wouldn't even tell me what kind of adhesive I'd have to buy for his kit until I bought the glass. That was a big turn-off to me because I want to know the hidden costs.

I found some alternatives though. Here's a website where you can order glass for watches in any thickness and any diameter to within 1/10 of a mm of what you need. I'm sure there are many others: http://www.esslinger.com/watchcrystalsflatmineralglass.aspx. Edit: This place has them as well but 3x at a time and $15 minimum:


At the first website, they're about $2.50 vs $15 for the eBay kit. With shipping it comes to a whopping $3.50 to your door. I bet they would also be suitable for the crankcase oil sight glass if you got the right size.

I got some measurements with my micrometer. They're taken using my old (1986) plastic sight glass and old o-ring. Bike is a 1986 VN750, stock.

Stock plastic sight glass
Inside groove for o-ring: 21.3 mm O.D. average (slightly oval)
Ridges inside/outside o-ring: 22.4 mm O.D. average

Master cylinder:
Sight glass bore: 22.50 mm, dead on in 3 spots. I'm pretty confident on this reading. (your glass must be a hair smaller)
O-ring I.D.: 21 mm just touching (This is old and somewhat flattened)
O-ring backspacing: 2.5 mm from slotted readout face
O-ring thickness: about 3 mm deep

I'd suggest glass 2.5 mm (back of o-ring) to 4 mm thick (center of o-ring depth) depending on how much contact you want with the o-ring.

RTV is supposed to hold up to brake fluid. I plan to use super black because I have it on hand.

Photos of my installation when I get my glass in the mail. I'll try to remember to update this thread.

Jason




 

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Registered
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248 Posts
Nice Find!

I think I didn the ebay thing with mine, and it's just a piece of glass, nothing special.

I'm pretty sure I used Super Black as well. No problems.
 

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Premium Member
1985 VN700
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8 Posts
I know this is an old thread but wanted to say that the info provided, specifically the source on watch crystals, is invaluable. Just ordered some crystals in 22.4mm and 22.3mm (just in case) plus some o-rings from ebay. Will update on how it works out. 1985 VN700
 

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Premium Member
1985 VN700
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8 Posts
Ok, so this is an update to my previous post. I used a 3mm thick by 22.4mm OD glass from Esslinger.com with 1 each O-ring of 18mm ID x 22mm OD and a 21mm ID x 24mm OD. I first inserted the 18mm x 22mm O-ring into the sight bore then the 22.4mm glass. I next placed the 21mm ID x 24MM OD O-ring and very carefully tucked it between the glass and the sight bore. I followed with a 7/8" Internal snap ring (tight fit getting into the bore) to hold it all in place. Has been holding brake fluid (just sitting) for a week now with no leak. Hopefully this will hold up to vibration from riding. I am pretty confident it will. Parts cost $7.11 + Tax and shipping. Hope this helps others. Will follow up with pics soon after I paint the MC (I am crap Rattle Can painting). 1985 VN700
 
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