Topic: 1977 CB550K Air Filter Replacements?

[Maraakate]

I'm looking for a replacement air filter for a 77 CB550K.  4into1 is out of stock and it appears that the OEM is NLA.  I see the Uni brand can be sourced easily on ebay and amazon but is there anything else?  I'm concerned the Uni may change how the bike behaves unless it's well known that it's OK to use the Uni without having to do some adjustments.  Looking for plug and play.

[jdip16]

Common motor collective out of Texas

Sent from my LM-G710VM using Tapatalk

[Maraakate]

Wow, they got lots of goodies there.  Thanks!

[Scott S]

 I run the UNI on all of  mine.

[david 750f]

David Silver Spares has an aftermarket replacement filter as well.

https://www.davidsilverspares.com/CB550K-1977-USA/part_144994/

[Deltarider]

OEM filters for the CB500 are dead cheap there and last forever.

[bryanj]

500 dont fit directly into 550 as 550 has an oil vapour recirc system

[Deltarider]

I know, I know, I just thought it wise to mention that genuine Honda air filter elements are still around and as far as the CB500 don't cost that much. CB550 owners should be aware that originally the filter elements for the F and K models differed. Furthermore I advise CB550 owners to abandon that silly blow-by system that does nothing but possibly wetting/fouling your paper air filter element, plug the holes and reroute the breather tube as the Honda CB500 - 550 Shop Manual shows on p. 170. https://www.classiccycles.org/media//DIR_1653304/DIR_1653404/DIR_1653507/ecc6759db0a214d5ffff8825ffffe41e.pdf BTW, is that why CB550 owners turned to (inferior) foam filters? I hope to post a vid soon that demonstrates one can change the OEM air filter element within 12 seconds and that includes opening the buddy seat, removing the tool tray, the cover and vice versa. I don't know about the lifespan of the CB550s OEM air filter elements, but the bigger CB500 ones seem to live for ever.

[Sano]

I am curious as to why the UNI foam filter is considered inferior.  I have read about another forum member getting better Dyno results when switching from foam back to paper.  I believe the thinking was that the paper element flowed more air.  I thought the foam elements were supposed to flow MORE air (unless they are over oiled).  I am probably begging for endless speculation here, anyone have good info on this?

[Deltarider]

I recommend the genuine Honda filters. They do not restrict, filter way better than foam and can be serviced within seconds. A filterexpert informed me that when airfilter A filters out 99,8 % of the particles and airfilter B 99%, enginewear with B is already fourfold.
On my CB500 the genuine Honda airfilterelements last at least 15.000 miles and do not detoriate over time. That's not bad for a filter that costs only around $ 17,-. http://www.davidsilverspares.co.uk/parts/by-part-number/partnumber_17210323030/
Foam filters may do fine on lawnmowers.
Some may find it hard to believe but as a matter of fact paper filters get better in use. For this and more info: http://forums.sohc4.net/index.php?topic=98901.msg1102737#msg1102737
Can't believe so many want to risk it with Unifoam filters or whatever they're called, filters that already are inferior fom the start. None of the genuine Honda filters I've used, served less than 18.000 kms. As a matter of fact I still keep them in my basement as they still are not clogged and so filter at their best. And the best thing is: I can change my airfilterelement within 12 seconds and that includes opening the seat, removing the tooltray, etc. And time, my friends, is the only thing I cannot make extra of. So why would I spend precious time on oiling, getting my hands dirty and then have to worry: did I oil too much, too little?

[flatlander]

I am curious as to why the UNI foam filter is considered inferior.  I have read about another forum member getting better Dyno results when switching from foam back to paper.  I believe the thinking was that the paper element flowed more air.  I thought the foam elements were supposed to flow MORE air (unless they are over oiled).  I am probably begging for endless speculation here, anyone have good info on this?

i while ago i tested a uni filter against an OEM paper filter on the dyno. that was with a built-up engine with optimised head flow. with that, i got better results, i.e. more air and higher hp numbers at high rpms, with the paper filter.
however, the engine design needs to be able to support this and i believe with a stock engine the difference will be tiny, i.e. the uni should be able to support the required flow, at least up to reasonable rpms. but paper filters are easy to find and quick and cheap to replace so why bother...

in my engine, i am now using the original paper filter still, and replace it every 10k km. after that it also reduces flow which can also be measured. again, that's with my high flowing engine - with an original one longer replacement intervals may be fine.
what may flow as well or better than the paper filter, and not need replacement is a single k&n pod on the original plenum which is what i want to try next.

[Deltarider]

what may flow as well or better than the paper filter, and not need replacement is a single k&n pod on the original plenum which is what i want to try next.

If you refer to that big oval filter that K&N decades ago had for the CB500 (R 82) and CB550 (R 83), it may well be the only filter that constructionwise, at least in my view, may give a slight improvement. Be it at the price of a considerably increased intake noise. If I owned a CB550, I would abandon the blowby gas route's last part towards the airfilter and I would try if maybe the bigger OEM CB500 filter element would also fit in the CB550 airfilter case. Mine seem to live forever. But on a CB500 there's no chance its filter element will ever be wettened/fouled by a blow-by gas system, because there is none.

[flatlander]

If you refer to that big oval filter that K&N decades ago had for the CB500 (R 82) and CB550 (R 83), it may well be the only filter that constructionwise, at least in my view, may give a slight improvement.

yes that's the one i mean. i have one of them somewhere in the basement, in its original packaging.

and i've never had any trouble with the blowby gas system on the 550. keep that sponge filter clean and there's nothing to worry about. that's actually one thing that puzzles me about the k&n installation instructions: they tell you to route the breather tube directly into a port after the filter, into the plenum. that's sucking all the blowby incl. crud onto the back of the valves which i'm not sure is such a good idea. could just leave it vent to the open air, of course.

[bryanj]

All down to emission regs, venting to atmosphere is an offence if it was on recirc in the first place. The Honda system recirced into the middle of the filter so went straight to intake

[Deltarider]

The Honda system recirced into the middle of the filter so went straight to intake

Yes... in an ideal world. When the engine sneezes back however, it lands in the filter. I have seen several CB550 airfilter elements that had that typical soft (moist) and often brown, oily spot. Maybe, if you check regularly, you can prevent problems. I personally would not like anything else than air and aerated fuel to hit the back of my inlet valves. Other stuff just doesn't belong there.

[Maraakate]

The ones at common motor collective look good, but they state there are two sizes for CB550.  Not sure what size I need and what the size differences are.  I emailed them about the sizes between small/large hole but they never replied.  Can anyone tell me the measurements?

[Deltarider]

Consult CMSNL's site. They are usually accurate with the pictures. https://www.cmsnl.com/honda-cb550-four_model14345/

[Maraakate]

They don't have dimensions listed, but it's really cool to see that have some NOS parts particularly for the carbs if I should ever need it.

[Sano]

  Thanks to all for the thoughtful responses.
   I do have something to add to the discussion about the blow-by recirc. system being evil.  One thing I realized after looking at the system carefully is that the low pressure environment DOWNSTREAM from the filter element draws blow-by gasses out of the motor.  This is a good thing as these gasses are corrosive and should be evacuated.  Venting to atmosphere will not do this. I hadn’t considered backfires possibly soiling the element but your motor shouldn’t backfire.  If the filtration is better with paper then I am changing back to paper (I live in the desert and super fine silt blows everywhere)
  Regarding the gunk getting baked onto the intake valves, yes, some of that is possible BUT those gasses have had the larger particles precipitated out by the screens/foam/ snorkel in the bottom of the air box and diluted by the gas in the gas/air stream (unlike what happens in direct injection engines)
  The more I learn about the importance of the intake SYSTEM the more I appreciate the Honda design.

[Deltarider]

... I do have something to add to the discussion about the blow-by recirc. system being evil.  One thing I realized after looking at the system carefully is that the low pressure environment DOWNSTREAM from the filter element draws blow-by gasses out of the motor.  This is a good thing as these gasses are corrosive and should be evacuated. Venting to atmosphere will not do this. ...

But the riding wind will do just that on models that had the tube venting to the atmosphere, as is shown in in Fig. K2-1 on p. 170 of the Shop Manual http://manuals.sohc4.net/cb500/service_manual/HSM500550_15.pdf . And the corrosive gasses are right there again as soon as the old ones have been evacuated, don't you think? Not to mention that the new gasses actually push out the old gasses.

  The more I learn about the importance of the intake SYSTEM the more I appreciate the Honda design.

IMO it was a poorly designed and flimsy adaptation for an already existing CB550 model*, just enough to satisfy the EPA. The 'system' (don't make me laugh) does nothing good for your engine. I myself appreciate much more the simple tube that Honda had positioned thus genial that the riding wind could take care of transporting the gasses to the rear.
Some here have argued that it was all about poisonous gasses, dangerous to the environment. That's not how I remember it. It is true: it is nasty stuff but - correct me if I'm wrong - originally it was more about getting rid of those nasty oil tracks on the roads. And that was a very good thing ofcourse.
* On later models like the CB650 it was much better.

[rosewood]

What are peoples thoughts on a catch can type set up before the breather pipe is fed back into the bottom of the airbox? best of both worlds?

Or even a oil/air separator that is used on a compressor airline...

[Deltarider]

Correct me if I'm wrong, but wasn't the system on the CB400F already an improvement?

[rosewood]

I'm sorry Delta I am not familiar with the 400f set up, I thought we were discussing the 500/550?

[Maraakate]

We are, and nobody has still said "hey this is a drop in replacement for 1977 CB550K".

[FourUsTry]

https://www.davidsilverspares.com/CB550K-1977-USA/part_144994/
https://www.common-motor.com/honda-cb500-cb550k-cb550f-air-filter  (choose correct Sub-Model)


Yes, these are drop-in replacements.

[Deltarider]

I'm sorry Delta I am not familiar with the 400f set up, I thought we were discussing the 500/550?

My point is that when you look at the design of the one on the CB400F and also the one on the CB650, you could conclude that Honda had reasons to improve on the old type (on the CB550s) that maybe was not so satisfactorily... And  from what I have seen, I know it wasn't...

[Deltarider]

We are, and nobody has still said "hey this is a drop in replacement for 1977 CB550K".

Sorry I'm not able to say what you wanna hear...  I thought anybody would know David Silver. In the meanwhile FourUsTry has served you. But maybe you still want something cheaper?

[Maraakate]

No, I need to know what is the size of the big hole vs small hole.  The price is about what I expect from all these links.  Nobody has listed dimensions and emails have fallen on deaf ears.  *shrugs*

[Deltarider]

You could do some research yourself first and use a parts finder like: https://www.hondaparts-direct.com/oempartfinder?aribrand=HOM&arian=motorcycle
Enter the parts number and the program will show on what models that particular part was.
Am I right to assume that yours is a K3? What exhaust system is on it? OEM or some aftermarket 4 into 1?