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O-ring sizing?

Fuel System: Gas (Petrol) tanks, Carburators
Dana01
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O-ring sizing?

Post by Dana01 » Mon Dec 06, 2010 9:17 pm

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

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brewsky
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Post by brewsky » Thu Dec 09, 2010 11:40 am

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
66 dream, 78 cb750k, 02fz1, 09 wing

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flathead
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Post by flathead » Thu Dec 09, 2010 12:51 pm

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
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Post by Dana01 » Thu Dec 09, 2010 1:08 pm

Thanks Flathead & Brewski ... good advice.

This o-ring sizing tool looks fun:

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

1966/7 CB-77 Red of course
1976 CB-550F (project over-budget and under-funded)
1985 GS-450S (Land Speed Racer)

bikedoctor99
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o ring sizing

Post by bikedoctor99 » Sun Dec 12, 2010 12:26 am

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
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Post by Dana01 » Sun Dec 12, 2010 9:44 pm

Thanks for the source BD99. BTW ... properly sizing an equal replacement part doesn't necessarily mean it's the improper part.
Last edited by Dana01 on Wed Dec 15, 2010 2:51 pm, edited 1 time in total.
Dana

1966/7 CB-77 Red of course
1976 CB-550F (project over-budget and under-funded)
1985 GS-450S (Land Speed Racer)

bikedoctor99
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Posts: 154
Joined: Sat Aug 14, 2010 7:11 am
Location: North Jersey

o-ring sizing

Post by bikedoctor99 » Tue Dec 14, 2010 10:56 pm

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.

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