Viton O-rings for oil service

[RickKean]

All the old O-rings I've observed on my project have suffered from compression set, and I'll be replacing as many as I can with general purpose Viton O-rings. I've found some Ebay vendors, but now realize that I'd been unclear about which diameters are in the Honda Parts listings...

After measuring a Crankshaft Cap and it's O-RING (5.5X1.5) 91301-216-000, it appears to be (Inside_Diameter X CrossSection_Diameter); correct?

We always used Viton O-rings during Corvair builds, and I figure they should work well on any air-cooled engine. Anyone else wanna share their experience using Viton O-rings for oil service?

Any CBXClub members who can recommend, and/or, better yet, have stock in Viton O-rings suitable for CBX oil service?

Thanks
Rick

[Limey01]

Www.mcmastercarr.com. I work on industrial gas turbines and can generally buy a pack of 25 from McMaster for the same price the OEM wants for one o-ring and the same probably goes for Honda. Viton, 75 Durometer A is a good choice for most applications. Metric o-rings are generally specified by ID X crossection diameter whereas inch o-rings are usually specified by a “dash” number which is an SAE standard.

[RickKean]

Thanks Limey01 for the McMaster-Carr reference; their offerings fill a few gaps :)

Any insight regarding using O-rings that are close to, but not an exact match to the CBX spec? For instance, cylinder base O-rings are spec'd 69.8x2.0, but McM-C offerings are a 5-pack of 70.0 x 2.0, or custom 69.5 x 2.0... Is the Viton O-ring seal more affected by slightly stretching an O-Ring that's 0.3mm under ID, or by using a slightly looser +0.2mm over ID? My wallet prefers the larger 70.0 x 2.0 route. +0.2mm over 69.8mm ID doesn't seem like much of a mismatch; 0.628mm (0.025in) circumference increase.

Any rules-of-thumb, or war stories of note?

Rick

[daves79x]

If you have the time and inclination to search replacements, go for it. But I and most of us, I think, just order those special O-rings from Honda. They are all still available, as far as I know. The originals lasted until it was torn apart, I suspect identical Honda items will outlast most of us. If saving money is an issue, the cost of these is a drop in the bucket compared to rebuilding an engine. Just my experience and IMHO.

Dave

[RickKean]

Understood; all counts. Initially I may just use Viton for the oil hose ORB's.

Still curious re: slightly stretched vs little loose. My problem; workin' it.

Rick