ESR exhaust flange O-ring size

[wilkin250r]

So I wanted to look around for new o-rings for my ESR exhaust flange, and I found a whole lot of people talking about them, but I never saw anybody post any specific sizes.  It was almost like a government conspiracy.  Not that I have a problem with ESRs prices or availability, I just wanted to look for maybe thicker rings, or different (more expensive) materials.

So I'm going to share my thought and findings, because I couldn't find the information anywhere else.

The o-rings I got from ESR are a hair over 0.100" in width, and since 0.103" is a fairly common width for o-rings, I'm running with that assumption.  It's either that, or assume they are metric, and I just don't think they are metric.

It's kinda tough to get an exact ID and OD on o-rings this large, because they don't hold a perfect shape at rest, they're kind of an oval.  I tried measuring the largest diameter at rest, and the smallest diameter, and finding the average.  I'm coming up with about 1.866.  This is subject to a very high degree of error.  This would mean the OD is about 2.072" (by calculation, not measurement)

My calipers don't fit exactly in the groove of my flange, but I believe I'm measuring a diameter of 1.942".  I know I'm going to want my o-ring ID to be smaller, to ensure a tight fit.  The width of my groove is about 0.120"



So I went through charts of o-rings, with the basic assumption these are standard size.  3/32 is a common o-ring size at the previously mentioned 0.103" width, and looking for the ID and OD to match closest to what I was measuring.

The end result is I believe these are a standard size #134 o-ring.  Standard dimensions are 3/32 width, 1-7/8 ID, 2-1/16 OD.  Actual listed dimensions are 0.103" width, 1.862" ID, 2.068 OD.  These are just a few thousands off from my actual measurements, so I'm pretty confident.

[2Nubs]

I like this idea. The extra thickness might very well seal these pipes up without the need for RTV. My R is a splooge making machine right now. I had planned to use RTV, but I will gladly try to source some O rings for us to test out.

[The norm]

I use orings and rtv to make a good seal

[wilkin250r]

Based on their price and temperature requirements, I'd give it a 98% certainty these are standard hi-temp silicone.  Anything more exotic and high temp is significantly more expensive.  Kalrez o-rings around that size are about $50 per o-ring.  I'm actually not opposed to spending that kinda money, but not before I do some more testing.

McMaster has a large selection of 0-rings.  A standard #924 is a little thicker, but also smaller ID and OD, so I don't know if I want to stretch them that much.

A #225 o-ring might work, but it's a little thicker than I want.  It's listed as a 0.139" thickness, and the groove I have only measures 0.120".  That might be a tough squeeze.

[Hawaiiysr]

A little unorthodox but I use tire plugs.

[hickwheeler]

I buy the o rings for the KTM 300 and 250. They are thicker. I usually have to grease them to slip the pipe on. A little patience helps too. Seems to seal good with no rvt. You kinda have to stretch them over the flange

[2Nubs]

That is awesome info Gene. I think I will go that route.

[wilkin250r]

I buy the o rings for the KTM 300 and 250. They are thicker. I usually have to grease them to slip the pipe on. A little patience helps too. Seems to seal good with no rvt. You kinda have to stretch them over the flange

Send me a link (or part number, or something) and I'll order a couple of those o-rings and measure them, I'll find out exactly what they are.

[wilkin250r]

On a side note, a metric o-ring 3x47 looks to be a perfect size (3mm width, 47mm ID).  By the specs, it's slightly thicker than the #134, (0.118" vs 0.103") and nearly the same ID. 

Problem is, metric o-rings just aren't as common, and exotic materials even less common.  McMaster doesn't carry them in a silicone, but they DO carry them in a Viton, which has nearly the same upper heat range, and similar price.  I think I'm going to get me some.

My current experiment is running this 250r with no RTV, just new o-rings.  It previously leaked with o-rings and copper RTV, so we'll see what happens without the RTV.

[hickwheeler]

https://www.motosport.com/oem-parts/part-number/0770440030

Looks like it is 44x3

[wilkin250r]

https://www.motosport.com/oem-parts/part-number/0770440030

Looks like it is 44x3

And they look to be Viton.

I think you might be better off with a slightly larger inner diameter.  I measured right about 1.94 inches for my exhaust flange o-ring groove ID, and 44mm is about 1.73, meaning your o-ring is almost 3/4 inch too short for that length.  Not terrible, because you actually want it to stretch a little, but it means if your o-ring gets hot and cracks in one spot, you now have a 3/4 gap as it rips and withdraws.

McMaster sells Viton o-rings in 3x47 (1.85" ID), 3x48 (1.89" ID) and 3x49 (1.93" ID).  I might pick me up a set of each, package of 5 is less than $10.  Slightly more expensive than the silicone, but I'm certainly not going to complain about spending $6 instead of $4.50 for a set of o-rings on my exhaust.  And who knows, the Viton might hold up better than the silicone, even though the temperature specifications say it won't.

[hickwheeler]

I have not had one go bad yet. They usually get messed up taking the pipe off. Because they get soft

[Tbone07]

Ok I finally found the ones I ordered from McMaster Carr awhile back.

Part #1283N151-----3/32" W, 1-7/8 ID, 2-1/16" OD Viton rings

^^^that's what I'm using at the moment and they seal up well.

I also bought Part #1283N97, 1/8" W, 1-7/8" ID, 2-1/16" OD.

^^^These were too thick and I couldn't fit my header on. But I suppose I could have put more effort into it and made it fit. I can't remember it's been so long since I looked at my poor girl.

[wilkin250r]

Ok I finally found the ones I ordered from McMaster Carr awhile back.

Part #1283N151-----3/32" W, 1-7/8 ID, 2-1/16" OD Viton rings

Those come up as a Silicone, not Viton.  Same as I described in my first post, size #134.

[wilkin250r]

So, I'll admit I haven't been super motivated on this project, I still want to try a few styles of o-rings I mentioned earlier in this thread, but I haven't gotten around to it. 

But I CAN give you a slight update.  I stated in post #8, I assembled the pipe with just standard o-rings and no RTV.  After about 5 hours of ride time, we have blown through the rings and the pipe is leaking again.  This doesn't mean that everybody will have this exact same experience, but for me, I'm going to try some new things.  I'm on a quest for a leak-free pipe.  It's a long quest, obviously, but a quest all the same.