Aiboxes and airfilters for CB500/550

[Erny]

Hi all,

I have CB550K1 (type 374) import from US that has rather specific (in Europe) airbox and also air filter. Part diagram for my CB550K1 US model : https://www.cmsnl.com/honda-cb550-k1-four-1975-usa_model466/partslist/F++05.html#.YhgS0eiZOMo

It is difficult and expensive too to get new filter. Genuine very hard to find (and expensive) and alternative/repro too. CMS does not have them anymore.

So, I start to consider changing whole airbox to other type (European?) that will solve this problem...

Does anybody have good overview what is the "best" option to look at? I mean what airbox(airbox housing)/filter I should be serching for?

Thanks for your ideas

[Trigger]

You don't need a new air box, just use a 550 F1/2 air filter 

[Erny]

so, simply buy 17210-390-P00 ?

I did not find any compatibility with 17210-374-P00 or 17210-374-003..

But would be great if it fits!

[Erny]

for example, this one? https://www.ebay.de/itm/124801958267?epid=1014623385&hash=item1d0ec6c17b:g:nJ8AAOSwOupg5dEW&shqty=1&isGTR=1#shId

[Trigger]

If you look up a picture 390 air box it is identical to a 374. Even the cover,element 374 shares  the same part number as the F1/2

[Trigger]

https://www.cmsnl.com/honda-cb550-k1-four-1975-usa_model466/housingaclnr-elem_17313374003/

https://www.cmsnl.com/honda-cb550f2-super-sport-550-four-1977-england_model17121/case-element-seal_17313390780/

Looks the same to me 

[Erny]

yes, but if it is the same, why the hell Honda does not show it is?
Honda would either use 374 code for 390 model or says 390 parts supersedes 374 one... but this is not the case.

[Trigger]

You must think outside the Honda parts manual  The 550K3 has the same air box but, has a different filter but, that is only because of the length of the pipe on the cover'element. The F1 air box is different to the F2 but, it is only a foam pad on the outsides.
I know lots of Honda parts that have the same part number but, look different and lots of superseded parts that may fit but, look different to the original part 

I could of advised you to replace your air box with a CB550F or a CB550K3 but, that would of been a waste of money and time     

[Erny]

Great,

so conclusion is that I can buy F filter and it will fit into my airbox, for example this one https://www.ebay.de/itm/124801958267?epid=1014623385&hash=item1d0ec6c17b:g:nJ8AAOSwOupg5dEW&shqty=1&isGTR=1#shId

[Trigger]

If you look up the difference between the 374 and the 323 filters, the only difference i see is there is a hole in the bottom of the 374 so, the tube can fit.
There are a few differences between the 374 and 390 filter but, i think with a few mods it should fit.

[deltarider]

If your (beautiful) bike was mine, I'd try the CB500 OEM airfilter element. Filtering area seems oversized compared to the 550 ones and they live forever. You'd have to reroute the crankcase breather tube though the way the CB500 has.

[Oddjob]

I'd second that. Ditch the recycling system of the 550 for the simple and more direct system for the 500, just vent it to air. You'd have to use the 500 filter or the hole in the bottom of the 550 filter will just let unfiltered air into the engine.

[Erny]

I plan to re-route breather hose as '76 550K had (see attached pic).
But I already bought that 550F filter from ebay... let's see how it will fit.

Will report back

Thanks for your advices/opinions

[deltarider]

Thanks to Nurse Julie*, we now know that that pic is incorrect (an error by Honda) and that it is actually the drain tube coming from the bottom of the airfilter case. Honda has had me fooled for years and also has left me wondering why nobody has ever seen a CB550K2 with what is suggested in Fig.K2-1.
The origin of that error may have to do with a CB500 model which was also assembled in 1976: the CB500K2 (ED, F, G) aka GENERAL EXPORT. Note that all modifications in p.170 also apply to that particular CB500K2 model and that model still had the conventional routing of the tube in real life.
Another possibility is, that at the time the CB550K2 addendum was composed, Honda was unaware that the US, where the breather system was law, was to be the only country where the K2 would be marketed. Maybe a CB550K2 GENERAL EXPORT at that time was not of the table. 
Now that you have that air filter element, I would either plug the hole in the bottom of it or, when you prefer to have it as designed, maybe not have the oil level higher than halfway the dipstick, like the Germans and also somebody in the international forum have suggested.
This German shop has all: https://www.cb-four.de/cgi-bin/shop/__CB-550-K-F/Verschleissteile/_04.08.html The mere changing of the middle number into -404- has not much significance. Back then, when the K3 was lauched, Honda has renumbered lots of parts to: -404-. Some parts were still the same  as before however.
* starting here: http://www.sohc.co.uk/index.php/topic,27043.msg250107.html#msg250107

[Sesman]

Now I’m really confused. Which models breath to atmosphere, which models breath to the airbox. There is no mention of the intake manifold drain….perhaps that’s not relevant to the topic.

Honda made an error…never🤔