Topic: Cb550k -087A carb help

[Ms Tokyo]

Getting into further dissection of my barn find and discover that the #3 inner carb has a broken fuel line nipple. First, I am confused as to where this connects because the manual does not show a thing. Second, can this be repaired or am I better off searching for a replacement carb body? Photo shows both #2 & 3 carbs with an intact and nippleless body.

[TwoTired]

Those aren't fuel line nipples.  They are carb bowl vent line nipples.  Pressed in.  A broken one needs drilling out.  You'll need a donor for a replacement.  Might be able to make a functional replacement with some ingenuity.  Otherwise, donor carbs.
It will run without them.  Connected hoses route down in front of the swing arm.  The long hoses help keep dirt out of the float bowls.

Cheers,

[Ms Tokyo]

Thank you! I didn’t think they were for fuel but couldn’t think of what to call them. Any thoughts on what I may be able to use to rig something up? If I drill the broken one out maybe tap and find a small threaded elbow of some sort?

[TwoTired]

Find the replacement before drilling.
Measure the nipple diameter of a good one.  Your replacement should be the same, and a right angle.  I think you're in for a parts search.  I've never had one damaged there before.  So, I don't have a ready source.  They aren't meant to be routinely removed.  You'll just have to find something to restore function.

Once you find it, make the carb hole sized to fit what you want to stuff in there, with an airway passage.

Field engineering!

Cheers,

[Bodi]

LLoyd is right as usual. The fuel galleries are under the undrilled larger "holes" just above where the bowl would be. The vents just keep the bowls at atmospheric pressure to let the carbs work as Mr. Keihin planned.
Most old bikes I see have no tubes attached to these and they seem to work OK. If several things go wrong at once it may be possible for fuel to dribble out of one onto the hot engine (not ideal) but you'd have bigger problems by then.The centre hole visible in the pic where the nipple broke off is pretty small... not much (a really really small insect?) could get in there and there's no suction to pull dirt in.
So it won't cause any trouble to leave it as-is.
The stub is just pressed in, I have removed these nipples with pliers and they're rather tight in there... you can try drilling, tapping, and using a screw to pull it out. Likely you will have to drill it out completely, nice of it to have a centre hole to guide the drill.
Replacement... hmmm. You might find something that will work at a model steam engine parts supplier? Someone with a supply of carb parts might have a original one for you. Easy to make something from brass if you have a small lathe. You can get brass tubing at hobby shops but it won't bend tight enough for the space available.
Personally, for a rider bike - not a show bike or concours restoration - I would leave it. Even with a show bike I might just glue a hose to the body that looks like it's connected, nobody is likely to have a mirror to see up between the middle carbs to check that it's correct.

[Ms Tokyo]

Body, thanks for your insight, you made my day!  I am moving forward without replacing at least for the time being.  Everyone’s advice is greatly appreciated.

[Ms Tokyo]

After soda blasting this carb, I’ve discovered that the fuel tube was corroded pretty bad and about a quarter of the o ring is exposed. With the combination of this and the broken bowl vent nipple, I’m in the market for a new 087a carb body.  I thought I had found one but it turned out to be an 022a. They look identical. What are the differences?

[Deltarider]

None. You can use them. They'll work fine. We never managed to establish what the difference between the 087A and 022A carbs is. Maybe, maybe the jet needle was positioned differently. The 022A carbs were on the CB550 and CB550K1, the 087A on the CB550K2 exclusively.
Here's a question for you to help us with our ongoing research. Could you unscrew an airscrew (in the side of your 087A carb) and inform us whether it is the crossdrilled type with an open tip, or the solid one?

[Ms Tokyo]

Cross drilled open tip is what I have. Carb body stamped 087A. So to clarify, you think I can interchange one 022A with three 087A’s and have no issue?

[Ms Tokyo]

Or is this salvageable? Leaf spring in bowl is going to hold it in place along with o ring.

[Deltarider]

I'm afraid not. Extra, not metered fuel can pass there and will greedily be sucked into the combustion chamber by the down going piston which will result in an overrich mixture.

Cross drilled open tip is what I have.

So far all that have the 087A carbs - that we have asked - have the same cross drilled open tip airscrew, so you're no exception. Reason I asked, is, when you study the CB550, K1, K2 Parts List*, you will learn that the only part in the 087A carbs that's listed as different (and so would explain the different carb number) is the airscrew. But... sofar nobody reported they actually have them, which lead us to believe that what was planned, maybe never has been materialised. Leaves the theoretical possibilty that maybe the jet needle was hung differently. So far we have no reports that confirm this.

Carb body stamped 087A. So to clarify, you think I can interchange one 022A with three 087A’s and have no issue?

If you have a complete rack of 022A, why not change the rack in total? If you don't have a complete rack, you could use just the one, provided it's exactly the right one to position in there. In other words: is it a #1, #2, #3 or #4? If you have all carbs on the table with the floatbowls removed, you could verify the jet needles are all hung equally. It's not difficult. When you remove the main jets, you can see the tips of the needles. You could use a simple measuring caliper to check. No need to open the top lids. Not yet.
* Page C10 Ref No. 7 in http://www.honda4fun.com/pdf_parts_list/pdf_spac550/CB550-K0-K1-K2/CB550-K0-K1-K2_04.pdf

[Ms Tokyo]

I do not have any spares at the moment so I wanted to confirm that a 022A could interchange with the 087A’s if I found only one. It is going to be a pain in the arse to find the one I need (inner). If you have any thoughts or suggestions on where to source one, I’m all ears. Thank you!!

[TwoTired]

The carb bodies are the same.  The number stamped on them referred to the parts use inside them which preformed fuel mixture tailoring for the application they were used in.

If you used all the parts from a 087a carb in an 022a stamped body, it should be restamped 087a.

Cheers,

[Deltarider]

Forsaid page in that parts list does not mention any other difference in brassware than that airscrew. Strangely enough so far nobody with 087A carbs (that we have asked) reported to actually have that particular airscrew (which the CB550F models do have, btw). All the other brass partsnumbers are identical to those in the 022A carbs. But there's no harm in checking me by having a close look at that page.
What we don't know for a fact, is, if there isn't any difference by chance in the shape of the venturi. But personally I estimate that chance very little indeed. I would exchange 087A carbs for 022A carbs without a shadow of a doubt they will function the same.

[Ms Tokyo]

I was able to find a substitute 022A rather quickly. Thanks for everyone’s help. I’ll report back if things do not line up as planned.

[Deltarider]

Not bad. Congrats. The 087A you showed in the pic, looked pretty awful anyway.