1983 GS850g air equalizer o-ring

[Guest]

Hi all,

I'm planning on replacing the fork air equalizer (balance?) o-rings on my '83 GS850g. There are 4 of them (2 on each side). I was hoping to buy the o-rings before I tore everything apart, does anyone know what size they are? I've attached a picture for reference.

Thank for the help!

orings.jpg

[Burque73]

No idea what size they are, but you can just order OEM and not have to worry about getting the right size from somewhere else. Assuming they send the right part that is.

https://www.partsoutlaw.com/oemparts...g-stem-model-d

Crap, never mind. #13 in the schematic isn't even available.

[Rijko]

CMSNL charges 5 euro per o-ring.
That would make me wonder about alternate sources, too.

[Burque73]

It looks like Bikebandit has them available. I just plugged in ship to Canada and was floored by shipping costs. $21.76 plus $30 for international shipping, no wonder you're looking around elsewhere.

I'll be curious to know if you're able to separate that part from the fork tubes and how you did it. I had one heck of a time with them when I replaced the springs last year. Never did get the things apart. At least the fork seals are still good.


Here's a thread I started on that repair.

https://www.thegsresources.com/_forum/showthread.php?255443-Spring-time-83-850G&highlight=

[Guest]

Burque73,

Thank for the info.

I attempted to change the fork oil last year and I had some trouble pulling the forks off too. There are no retaining rings or anything of that the sort. I basically just pulled the forks through the air balancer. It was a little hard at first but it got easier once things started moving.

The real problem came up when I tried to fill the correct amount of oil. As far as I remember, it was 140 mm from the top of the compressed fork. When it was filled to the correct level, oil would leak out from a hole on the form that is located where the air balancer normally sits. So, I figured I would drain all the oil, reinstall everything and use the correct volume of oil (251 ml) instead of the height. When I did that, oil started to leak from underneath the air balancer. At this point, I'm thinking maybe the o'rings are worn and need replacement. If you have thoughts, I'd appreciate them.

Thanks,

[bwringer]

That... is a damn good question.

I replaced these with OEM on my '83 eight fiddy G a few years ago, and the o-rings were available at that time. I don't recall any particular difficulty other than they were a little fiddly and getting the fork tube back in was a little harder with new o-rings.

The size definitely isn't embedded in the part number.

We know, of course, that the fork tube is 37mm OD.

If you can measure the depth and width of the o-ring slot, we can figure out which metric o-rings are needed. McMaster-Carr sells 37mm ID o-rings in 1mm and 1.5mm cross-sections.

[Grimly]

CMSNL charges 5 euro per o-ring.
That would make me wonder about alternate sources, too.

CMSNL are a bunch of pirates.
I ended up getting seals from Fowlers UK, for 2/3 the price and half the shipping cost.

[Guest]

That... is a damn good question.

I replaced these with OEM on my '83 eight fiddy G a few years ago, and the o-rings were available at that time. I don't recall any particular difficulty other than they were a little fiddly and getting the fork tube back in was a little harder with new o-rings.

The size definitely isn't embedded in the part number.

We know, of course, that the fork tube is 37mm OD.

If you can measure the depth and width of the o-ring slot, we can figure out which metric o-rings are needed. McMaster-Carr sells 37mm ID o-rings in 1mm and 1.5mm cross-sections.

Alrighty, I guess I'll have to tear it apart before buying replacements. Stay tuned, I'll do the measurements as soon as it gets a littler warmer around here.

[bwringer]

FWIW, you can definitely re-use these at least a few times.

Countless '83 GS owners have replaced steering stem bearings without even being aware of these o-rings. I'd squirt a bit of some sort of oil in there before disassembly to help keep them from sticking, and of course you want to make sure the outside of the fork has a light coating of oil before assembly.

[Guest]

That... is a damn good question.

I replaced these with OEM on my '83 eight fiddy G a few years ago, and the o-rings were available at that time. I don't recall any particular difficulty other than they were a little fiddly and getting the fork tube back in was a little harder with new o-rings.

The size definitely isn't embedded in the part number.

We know, of course, that the fork tube is 37mm OD.

If you can measure the depth and width of the o-ring slot, we can figure out which metric o-rings are needed. McMaster-Carr sells 37mm ID o-rings in 1mm and 1.5mm cross-sections.

I finally made some time to take the thing apart and do the measurements. The slot is 3 mm wide and 1.5 mm deep. So I was thinking of getting a 36 mm I.D. with a 2 mm cross-section. This way I'll have 0.5 mm interference fit on each side which equates to about 2.7%. What are your thoughts?

Thanks,

[bwringer]

I finally made some time to take the thing apart and do the measurements. The slot is 3 mm wide and 1.5 mm deep. So I was thinking of getting a 36 mm I.D. with a 2 mm cross-section. This way I'll have 0.5 mm interference fit on each side which equates to about 2.7%. What are your thoughts?

Thanks,

In doing the math and recalling my installation of the OEM o-rings, that sounds about right. You do need a little stretch, so 36mm ID is just about perfect on 37mm fork tubes.

I'd use Buna-N o-rings because they're slightly softer than Viton; I do remember that it took some wiggling and shoving to get the fork tubes installed past the new o-rings. I lubricated the fork legs with a bit of fork oil.

Let us know how it turns out!