O-ring sizing?

[Dana01]

Hey all. re. my 1966 CB77. Does anyone know the dimension for the o-rings which sit behind the carb. insulator block? (I'm still waiting for my part number manual to arrive.) I believe it's p/n 16173-260-004.

I really don't want to buy a 45 year old OEM rubber o-ring :0

I mic'd the groove and came out with 2.4mm x 29mm.

Grainger sells 2 sizes which are close: 2.5mm x 32mm, and 2.4mm x 27mm.

That means that the larger one will be 3.0mm too large, but the smaller one would be 2.0mm too small.

I figure the smaller size can easily stretch to fit the groove.

Thoughts before I order?

Dana

[brewsky]

You can spend all day on this site, they have so many specs you donn't even know which one to choose!
http://www.oringsusa.com/catalog/produc ... rhu8es1f10

[flathead]

Be careful putting a the wrong size O-Ring in the phenolic carb spacer. First set that I ever installed I used the "close enough to work" method and promptly busted the spacer with just a little torque on the 6mm studs. The material between the edge of the face groove and the ID of the spacer is very thin and will break out if theres more material in the cross section of the o-ring than there is cross section area in the groove.

Mark

[Dana01]

Thanks Flathead & Brewski ... good advice.

This o-ring sizing tool looks fun:

http://www.efunda.com/designstandards/o ... radial.cfm

[bikedoctor99]

the NOS rings that i've purchased from Nick@Ohio Cycle are fine, pliable and of course fit correctly. why risk an air leak or broken spacer? you can avoid problems and time by using the proper part.

[Dana01]

Thanks for the source BD99. BTW ... properly sizing an equal replacement part doesn't necessarily mean it's the improper part.

[bikedoctor99]

I understand that correctly sized o-rings should and would work, but for the time and effort to find an alternative replacement for a part that is readily available and reasonably priced doesn't make sense; I don't mean to criticize, but to me a major part of the challenge of these old babies is to find the parts at all- BTW knowing how to measure for a correct o-ring is good, thanks. One of the advantages of this forum is the networking that can shortcut many potential problems.