Author Topic: Cheap Float Bowl O-Rings  (Read 2576 times)

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Offline buswork

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Cheap Float Bowl O-Rings
« on: March 09, 2013, 09:42:01 am »
Hello Honda friends,
I decided this would be a great time to tear down my CB550 Keihin carbs before the season starts, but I knew I needed new float bowl gaskets. I looked around online and the cheapest I found was about $16/pc, or $64 for the set plus shipping. This got the fire burning in my cheapo heart so I decided to do a little research. Two of the old ones were intact and good enough to measure, so I pulled out my trusty caliper and got some numbers. From there, I searched o-rings, ANSI standards, materials, and prices. Here's what I found that got me a full set of float bowl gaskets for 96 cents, or, if you prefer, a 98.5% discount.

The float bowl o-rings, when doubled over are about 4.222 inches, or 8.444" circumference. A little math gives 2 11/16" or 68mm diameter. The cross section is 0.076 or about 5.64". This falls between AS568 standard sizes of -038 (2 5/8) and -039 (2 3/4). I found both for cheap at Since they're exposed to gasoline, I got the Buna-N Duro 70, which is rated for contact with petroleum products.

The -039 turned out to be way to big, kind of like when the old rings swell up over time, and the -038 were just a little too small. I had trouble at first getting them to seat while I bolted the carbs back down. I tried filling the groove with petroleum jelly to hold them in place, but the corners kept coming up. So I took a page out of the birthday party clown playbook. Similar to how you would stretch balloons to make balloon animals, I was able to get them to stretch just enough to sit nicely in the groove while I bolted everything together. I took the ring and held it between one finger on each hang, then for about a minute, applying about a pound of pressure, I rolled the ring until it stretched very slightly. Think like a false start signal in football.

I got the rings to seat with a little more vaseline and hopefully no leaks.

TLDR; Keihin CB550 carb float bowl gaskets: go to and order 038 B70 Buna-N 70 O-ring for $0.24 each instead of $16 from Honda.


Offline Honda550k

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Re: Cheap Float Bowl O-Rings
« Reply #1 on: April 03, 2013, 05:32:15 pm »
Thanks for sharing this. I just ordered 4 of them :)