Topic: Odd O-ring size for CB550K1 petcock inner assembly

[tkarahalios]

Hi all,

I am rebuilding my petcock for a 1975 CB550K1. It has the odd petcock without the sediment bowl on it as shown in the image below. I bought a Honda rebuild kit that came with everything I need except it did not come with the o-ring that sits inside the petcock assembly right behind the selector valve switch.

I tried to find the part number online but had no luck. It seems to be listed as part of the assembly and not have a separate number. I tried to measure it with calipers and I think its about 19mm inner diameter, by somewhere around 1.6-2.0mm cross sectional diameter. It's hard to tell because the o-ring has sat in there so long the cross section is not very round anymore.

Does anyone know what the dimensions for this might be? or a part number for it? Just wondering if anyone has gone down this road before. I'm just trying to avoid ordering different sizes to get it right since the only place I know of to order them sells them in bags of 50. (McMaster Carr).

Thanks.

[basic]

Check amazon for orings. Search by the as568 size. You can get a chart of sizes here: http://www.marcorubber.com/sizingchart.htm

A quick glance looks like it's close to a -018. Amazon has a set of 5 for 68 cents.

http://www.amazon.com/dp/B000FN0ZDO/ref=biss_dp_t_asn

Good luck and report back.

[Gene]

I have that same model petcock - another member was trying to rebuild his as well - and we found this out

"Re: Please help me identify this petcock

« Reply #21 on: June 30, 2015, 05:45:27 PM »
 Like I said....rebuild kits are  not available for that part. It was a faulty design and Honda went with something else after that year.
 Your best bet is finding a member with an old leaky one they've replaced and see if they'll sell you the handle.
 Still order the filter part, though."

You can go to that thread - there is at least a replacement in-tank filter available, but you're gonna have to wing it on the o-ring.

http://www.davidsilverspares.com/CB550K-1976-USA/part_70857/

I got lucky and found a replacement on ebay - but it's a one-year model petcock.

I'd be happy to mail you my old one if you think you can use any parts off it.

[tkarahalios]

Thanks guys,

I just ordered the o-ring "Basic" found on Amazon for me. What a deal. I get 5 of them shipped to me to arrive this Monday all for $0.69 and that includes shipping and handling since I have Amazon Prime. Unbelievable.

Gene, thank you for the offer. I have the rebuild kit you mentioned, and I dropped the parts in an ultrasonic bath my friend has. So, if the new o-ring I just ordered doesn't fix things I may reach out to you for your old parts.

Cheers and good night guys.

[754]

Is it a 75 ? I had a too big oring in mine., went smaller it broke....back to big one with screws backed off.
Not sure if original had an o Ring or square section ring..
Honda is known to use a lit of tween sizes on o ring cross sections..
 
To. Measure. Your flattened one  take the fat and thin measurement..average out the difference. Should close to the real size.

[basic]

hope it works.

the size suggestions was just given off your measurements. You may find it's better to go to a 100 series oring to get a little extra cross section. If this is the case, then a -116 is probably in order. It's 2.6 mm diameter vs 1.8 mm in thickness.
http://www.amazon.com/dp/B000FN0X54/

If the cross section thickness of the -018 is good but diameter is a bit off, the next smaller/larger is a full mm difference in diameter, so you may need to go to a metric o-ring.

[tkarahalios]

So it is for 1975 CB550. It looks kinda like a square profile but I think it's maybe the result of a 40 year compression set. I ordered the 018 size from Amazon. I'll report back what I find out when it arrives Monday. Again since it costs less than dollar with shipping it's worth trying...

[754]

If it was square, it wont have much roundness to it.