Searching for an 0-ring substitute for rear master brake reservoir

[dbtroudy]

I’m rebuilding the rear master brake cylinder from a ‘76 GL1000 LTD. I disassembled the brake body and separated the reservoir take and internal o-ring. Cleaned the o-ring at the reservoir 0-ring in Simple green and left it out on the workbench overnight. This morning I tried dry fitting the brake body, o-ring and reservoir cup together. I could not get the cup to slip past the 0-ring. After taking another look at the o=ring, someone previously has changed the o-ring out and used flat seal. I remember before I started, the tank reservoir was sitting up about 2 mm above the brake body.

I was planning to use a new o-ring anyway in the rebuild and went and checked to see if Honda still stocks the reservoir tank o-ring, PN 45516-371-003. I discovered that this part number has been discontinued by Honda The size of the o-ring (according to Honda) is 43.75X2.5mm. Does anyone know of a substitute PN for this o-ring? And is their a vendor that still stocks this size o-ring?

Don

[redglbx]

I believe that simple green is a mineral oil based solvent which is very bad for brake fluid components, just ruins them as you’ve found out. If it were me, I would buy a new rebuild kit and thoroughly clean all the components with alcohol or brake cleaner.

The reason being that the residue from the simple green probably has started acting on the installed rubber components already and will ruin the new ones as well if not cleaned well. You cannot expose any brake fluid component to anything mineral oil based, it will ruin the brake fluid rubber stuff, it only takes a trace amount. So if you cleaned the M/C parts with simple green, then all the rubber needs replacing, after cleaning with a brake cleaner. Sorry Don.

[Whiskerfish]

Last I knew replacement cup kits had the ORing with them.

[julimike54]

You can find a 'kit' to rebuild that here....

https://newmotorcycleparts.net/brake_pa ... _kits.html

about 1/4 to 1/3 down the page

[dbtroudy]

I was just hoping to find the 0-ring and not use a full rebuild kit. Someone in the past substituted a flat washer o-ring instead of the round 0-ring that was supposed to be used. While we are talking rebuild kits, here is an other source I have used to re-build the front master brake cylinder on a ‘79 GL1000. The picture is of the reservoir rebuild kit for the rear master cylinder.

Don

[pidjones]

I buy o-ring stock on eBay, cut to length on 45 degree and glue with super glue to make my own. Been doing it a long time for large hard-to-find o-rings. Lubricate with silicone vacuum grease to ease installation (the reservoirs are tight).

[flyin900]

Any 44 X 2.5 mm O ring will work from various online O ring suppliers. Just confirm you specs as I think Honda uses OD as their 44mm sizing spec, so measure your current O ring OD.

[dbtroudy]

I buy o-ring stock on eBay, cut to length on 45 degree and glue with super glue to make my own. Been doing it a long time for large hard-to-find o-rings. Lubricate with silicone vacuum grease to ease installation (the reservoirs are tight).

This is an interesting idea of custom making an 0-ring. How well does the super glue hold up?

[Sagebrush]

Go to a local John Deere dealer if you have one. They stock gobs of O-rings. Tell them what you need and see if they can match it. They are likely to find something very very close.

[dbtroudy]

Go to a local John Deere dealer if you have one

I wish - I live in Southern California - no one here drives a tractor.... There is a Tractor Supply out near where my kids live. I'll stop in and see if they have o-rings.

D.

[pidjones]

I buy o-ring stock on eBay, cut to length on 45 degree and glue with super glue to make my own. Been doing it a long time for large hard-to-find o-rings. Lubricate with silicone vacuum grease to ease installation (the reservoirs are tight).

This is an interesting idea of custom making an 0-ring. How well does the super glue hold up?

Haven't had a failure yet. Sometimes I sand the joint a bit after making it if it looks to have glue on the o-ring surface or is a bit misaligned. I really prefer Buna-N (nitrile) in most applications.

[redglbx]

All great ideas with one caveat. The o’rings need to be brake fluid compatible rubber which is EPDM or Butyl if I remember right. Normal buna-n rubber will begin to crack and fail when it’s exposed to brake fluid.

Buna-n rubber mineral oil o’rings exposed to brake fluid is not as bad as Nitrile brake fluid rubber exposed to mineral oil which will greatly swell and fail fairly quickly.

You must use the correct rubber o’ring, they are not all the same, you can’t just grab any ol’ o’ring, there is a difference !

(12-25-21) I went back and pulled my rubber manual to see what is recommended for a brake fluid application and see that EPDM, EPT, EPR, SBR & GRS are the highest recommended rubber for non-petroleum brake fluid o’rings. I hope this helps.

[BlueThunder]

Google the size and you'll find lots of vendors. Just make sure you get one that is resistant to brake fluulid.

[LuckyEddie]

I got lucky and was able to order one from CMNSL in Europe a year ago or so. I did have to sign up to be put on a waiting list for a while though. Worth the wait for the correct Honda part...

[Dr. Frankenstein]

FWIW, I've used Brakecrafters for a lot of my brake stuff; a great bunch of guys that will work with you and their stuff is Spot-On plug-n-play; well worth it for these hard-to-find parts. In my experience, if they say it fits, it fits. Quality parts too.