Topic: 1977 550f2 airbox

[corridoi]

Hi there,
I have a problem with my 550f2. When I opened the airbox I discovered it miss 3 parts! Nevertheless the bike runs, fast!
Looking at the the part list for cb550f2, they are n.19 (cover element), 20 (cover element seal) and 21 (element).

I found (almost) part n. 20, element cover seal, but the seller says it's ok for cb550k and cb550f1 and doesn't know if it fits on a 550f2.
Actually on my part list the code is 17351-390-780 and the part I found (but not yet bought) has the code 17351-374-003, as written on the 550f1 part list, even they looks identical.

Does anybody know if these part actually are different?

Thanks!

P.S.
I would attach a picture of the part list but I still have to write my first 5 post to be allowed to do it.

[Deltarider]

The parts you refer to are part of the breather system (blowby gas to be recirculated).
I remember that where I live many (dealers included) disconnected this system altogether as there was the risk the paper filter element got humid and was fouled by it. TwoTired will not agree but many here judged the device was not satisfactorily. In particular those who preferred to continue the use of the genuine Honda paper filter element (wise) choose to disconnect it and so did without this device and had it the way as it was on predecessor the CB500 Four.
For performance there are no negative effects if you disconnect it.
So my conclusion is the PO of your bike choosed to have it this way.
Wait a minute... Naples, you mean Italy? That could also explain why it is missing.
If you're Italian, you may have found the Parts List specially for the CB550F2 I've uploaded the other day. http://www.honda4fun.com/materiale-documentazione-tecnica/parts-list/parts-list-cb550 Allthough it doesn't specify, I would not be surprised if Honda Italia back then judged customers were better of without this breather thingy. After all, in Europe we had no laws on this. Not then and certainly not for motorcycles.
This recirculating of blow-by gas originally was manditory for trucks, later cars and then motorcycles in the US followed.
The Blow-By Gas Scavenging Device is described in the Honda Shop Manual 500-550 on p. 108-9 and p. 158-9. http://www.honda4fun.com/materiale-documentazione-tecnica/shop-manual
Don't worry about your English. I myself am here to learn English and believe you me, in no time you know words like obtuse and e-ven-tu-al-ly.

Ciao

[corridoi]

Thank you Deltarider.

I was on holiday and I abandoned my 550 for a month. Now I'm ready to restart with her.
Actually the airfilter i found on her tells me it wasn't a choice to disconnect the original system but just a rough replacement of an old airfiler. In fact, it is not a 550f2 airfilter, it hasn't any hole for the cover element n.19.

Now I have to choose what to do:

1) I just buy a new airfilter and put it in its place without the other parts we are talking about. Problem: the big hole where the air go in the airfilter does not match with the airbox hole from where the air is taken, just because without those parts the airbox is positionated lower.

2) I restore the original breather system (I would prefer this way, just to restore the bike at its origin) and then I repeat my first question about the matching between cb550k-cb550f1 and cb550f2 cover element seal:
"I found (almost) part n. 20, element cover seal, but the seller says it's ok for cb550k and cb550f1 and doesn't know if it fits on a 550f2.
Actually on my part list the code is 17351-390-780 and the part I found (but not yet bought) has the code 17351-374-003, as written on the 550f1 part list, even they looks identical.
Does anybody know if these part actually are different?"

Thank you guys!

[flatlander]

i can't tell you for sure if the seal will fit on the f2 - don't have one here to compare

the filter in the scavenging unit (part "element") and the seal plate have the same part numbers between f1 and f2. then, the "element cover" and seal have different numbers but as you say, look the same in the diagrams. if i were you and if the guy sells it reasonably cheap, i think i'd just get it as it seems quite likely that it will fit.

if you want to skip the whole scavenging thing as delta says, you could just prop up the filter from underneath so that its opening is aligned with the one of the filterbox.