Topic: 550 air cleaner breather tube

[reddyvv]

I'm doing some maintenance on my 75 K1 and when cleaning the air filter noticed some oil/water mixture at the bottom of the airbox. Obviously condensation and some oil blowby - no big deal. I thought the drain tube #31 was blocked but saw that it has a removable plug at the end. Problem solved.

I then noticed that the breather tube part #26 has no end plug on it so it can draw in unfiltered air.

I bought these tubes new at the time when restoring this from a basket case but for the life of me I can't remember the logic behind this. I checked online and pics show #26 doesn't come with a plug whereas #31 does.

Why would the airbox plenum #19 require a breather tube? Can anyone shed some light? What am I missing?

[bryanj]

It needs a tube to let any liquid out and i guess the length is worked out so no unfiltered air is draged in

[Rayzerman]

Not this bike, but more modern ones had a one-way valve in the drain hose... you could look for a rubber duckbill like they use on car a/c drains.

[jonda500]

Maybe originally one of them had a squeeze valve on the end? - I used the bite valve from a backpack water bladder on my 550F.
John

[Deltarider]

The 17335-323-000 TUBE ASSY., BREATHER is also on the CB500. I don't know about yours, but my OEM one has a little foam filter inside the thicker part. According to the parts lists, that thicker part is to be connected to the plenum's exit pipe.

[jlh3rd]

This parts page is from a first edition honda parts book, so the pics are different. This honda page shows it as a drain tube with that "squeeze" end.

[jlh3rd]

maybe this could work.

[Deltarider]

Jlh3rd, is that from some "F" model partlist? The OP was about a "K" model.
I recommend all CB500/550 owners:
to identify their exact model by comparing the engine- and framenumeber to those listed in the first 4 pages of the various CB500/550 parts lists. Good news is that you only have to do this once. You will have the model's original carbnumber, the colours and the 'area code' of yours as a bonus.
From then on consult the appropiate partslist for your specific model, paying extra attention to the proper 'area code' and possible modifications during the production of that model which will be indicated by serial numbers.
If then, there are still questions, come forward in this forum. Most of us are willing to help, but we appreciate if you have taken the first steps yourself. This can save us having to answer the same questions over and over again. Rest assured that any 'black swans' will have our special interest.

[HondaMan]

The 17335-323-000 TUBE ASSY., BREATHER is also on the CB500. I don't know about yours, but my OEM one has a little foam filter inside the thicker part. According to the parts lists, that thicker part is to be connected to the plenum's exit pipe.

Those little foam filters are what I've seen in the airbox drain hoses. Now 50 years later, they might be gone though? A small piece of soft sponge would provide a replacement, so long as it stays down in the tube.

[jonda500]

Re-read the original post - it is the plenum hose he is asking about, and the question has been answered - the plenum breather tube #26 is a drain tube and is supposed to have a little piece of foam stuffed in the thick end. The airbox drain tube on some 550's has a drain tube valve at the end...
John