Author Topic: CB350F Carburetor Insluator O-ring Size ?  (Read 985 times)

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Offline Dr. Frankenstein

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CB350F Carburetor Insluator O-ring Size ?
« on: October 07, 2025, 09:56:23 AM »
Does anybody know the complete specs for the carb holder O-rings on a CB350 Four? (Part Number 16173-253-004). I need O-rings, and the insulator itself mic's out at 32 ODx27 IDx2.4 CS, but all I can find as far as the dimensions go is "27x2.4.."   

Measuring the GROOVE, my micrometer meanwhile shows the dimensions as 32mmODx27mmIDx2.4CS...another spec I came across for the O-rings is 27 ODx22.2 IDx2.4 CS...which one is accurate? 

Would a 27x22x2.4 fit..?

Offline Dr. Frankenstein

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Re: CB350F Carburetor Insluator O-ring Size ?
« Reply #1 on: October 07, 2025, 10:34:50 AM »
Hi Ozzy - yes, you did, but I had already ordered some; and besides, the ones in the picture are not the right size - I'm talking about the O-rings that go on the carburetor mounts, or "insulators" -y'know, the carb boots that go on the cylinder head that you stick the carburetors on...those O-rings...

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Offline Ozzybud

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Re: CB350F Carburetor Insluator O-ring Size ?
« Reply #2 on: October 07, 2025, 10:43:44 AM »
They are the same as the valve cover caps i believe. Readily available
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1970 CT70  CANDY SAPPHIRE BLUE
1971 CT70H CANDY TOPAZ ORANGE
1972 CT70H CANDY EMERALD GREEN
1973 CL200 CANDY RIVIERA BLUE
1974 CB350F GLORY BLUE BLACK METALLIC
1973 CB350F FLAKE MATADOR RED
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Offline Rayzerman

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Re: CB350F Carburetor Insluator O-ring Size ?
« Reply #3 on: October 07, 2025, 12:19:19 PM »
The part description is 27 x 2.4, which is ID and profile.  That would make the OD ~32.  I always thought these were a little thin, and there appears to be room to squish.... in other words, a 2.5+ profile wouldn't hurt.  I bought some new aftermarket boots (I had cracks in mine) and used the O-rings that came with them.... I seem to recall I ordered some others of some fuel resistant type... will have to measure them up......
« Last Edit: October 07, 2025, 12:20:56 PM by Rayzerman »

Offline Dr. Frankenstein

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Re: CB350F Carburetor Insluator O-ring Size ?
« Reply #4 on: October 07, 2025, 02:31:31 PM »
FWIW I found these on Amazon: https://www.amazon.com/dp/B07W991ZLH?smid=A1THAZDOWP300U&ref_=chk_typ_imgToDp&th=1
I think these'll fit nicely.

I did measure the CB350F rocker arm caps against the manifold boots, and the rocker arm caps were too big/not the same size as the manifold boots; I'm anal like that...besides, $6.69 for ten nitrile O-rings beats the $8.95 apiece for the 'solid gold Honda' O-rings I've seen advertised online. I don't think my bike will care. Of course, if they're not a good fit, I will report.

Offline HondaMan

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Re: CB350F Carburetor Insluator O-ring Size ?
« Reply #5 on: October 07, 2025, 06:53:28 PM »
Normally, O-rings are spec'd by [ID] x [thickness]. Then the OD is already defined by default. ;)
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