Topic: 74 CB550 air filter oil separator.

[58webbing]

Having found out that the air filter oil separator bits are not available for my 550 I will have to make something. I propose to manufacture the part out of ABS so I can machine it on my CNC router. The missing part nos. are 17350374003 and 17351374003. (photos attached) The finished product will first of all have to work and fit rather than be an accurate copy of the original.
What I need to know are the basic dimensions of these parts ie. tube diameter and length, hieghts etc. The rest I can probably work out from scaling photos.
Any help in providing the missing info. would be really helpful. When I have made the part I can upload photos and the manufacturing files.

Thank you 

[Deltarider]

Do yourself a favour and forget about that breatherfilter altogether. Just reroute the breather tube as shown in the first pic. on p.170* of the Shop Manual Honda CB500-550 and be done with wettening/fouling your paper airfilter element. I've seen many filter elements with that typical soft (wettened) and often a bit brown spot.
* https://www.classiccycles.org/media//DIR_1653304/DIR_1653404/DIR_1653507/ecc6759db0a214d5ffff8825ffffe41e.pdf

[TwoTired]

Delta is deluded and doesn't have any useful experience with an SOHC4 fitted with the breather system, imo.

Yes, if you neglect cleaning the thin breather sponge, in cold wet weather, it will clog and spray bits onto the paper filter.  But, it is no big deal.  There is far more filter area than needed. And, if you shorten the stand pipe like later models employed it isn't any issue at all.  I know this from operating the set up (with the taller stand pipe, and the short) for 20+ years.   Delta doesn't have a bike with it installed, never has, either.  His knowledge base is hearsay, at best.  And he would have no clue how to find to the true cause to a system problem.

All modern vehicles with IC engines have some form of crankcase gas evacuator.  Its not just there for air pollution control, it also helps keep the crankcase clear of soot from piston ring blow by, and water vapor from blow by as well.  Neither of these you want in your oil supply.

In winter operations, when I noticed that brown mayo collecting at the oil dipstick, I also found the foam at the bottom of the separator plugged, too.  It was not just coincidence.  Clean the foam so it can breathe and do a good long run to get the entire engine unit hot, and the water emulsified oil around the dipstick vanished without an oil change.

I just finished a move, and all my spares are still in boxes.  If I'm able to find the right box, I can make measurements for you.
But, I'd recommend perusing EBAY for those metal parts, though. 

Regardless, I feel the rebreather offers far more benefits than detriment for this machine, as clearly the Honda engineers did, too.   All the bikes I have acquired where this device was removed, I restored with used parts. It is exactly what Honda intended.

The Honda manual reference previously mentioned, was a one year only modification for the 550.  It was an attempt to circumvent the EPA hydrocarbon emission standard that was going into enforcement for the 78 models.  The rebreather sucks hydrocarbons out the crankcase into the intake.  As Honda was having difficulty leaning the idle enough on the old style carbs, dumping hydrocarbons where the EPA wasn't testing helped get closer to requirements.  Note the 77 and 78 models all had the recirculation breather installed on US import models.  I don't have a 76 K model CB550,  I do have an F model CB550F, and guess what? It has the recirculator right from the factory.  I speculate that the high pressure 4 to 1 exhaust of the F vs the 4 to 4 system, helped idle emissions so much that bypassing the recirculator wasn't even necessary.  Both carbs and a high pressure exhaust were changed for the 77-78 K models, (which still had the recirculator installed as factory equipment).

I'll be back if I find my spares boxes for dimensions, or I dismantle one my bikes.

Cheers,

[Deltarider]

TT, why don't you give a lecture for all the now retired mechanics and tell them they have been doing it wrong all those years. That breather thing does nothing good for the running of the engine and as far as the environment... well, as long as the owner compensates by - for instance - not taking a noise producing, fossil fuel wasting petite airplane to the sky, where he has no business than to look st... st... special... mwah. Don't you like to look at things in perspective, every now and then?

[58webbing]

Thank you for the information thus far provided, it is most interesting and, lots to think about. I have always been of the opinion to connect the engine breather to the intake manifold at some point so as to keep the engine internals under negative pressure A to help prevent leaks and, B to help remove condensates.
 
I have scanned eBay together with other sites and have found nothing hence the request for dimensions.

I am supprised at the Honda mod as shown, as any oil that escapes will be directed at the rear tyre, not a good idea!

[bryanj]

That is not a mod it is how the 500 and early 550 were built. Honda only modified it to recirc after California gor paranoid! And it is not to give negative pressure but to stop hydrocarbon emissions

[TwoTired]

That is not a mod it is how the 500 and early 550 were built. Honda only modified it to recirc after California gor paranoid! And it is not to give negative pressure but to stop hydrocarbon emissions

The impetus was certainly emission control, Bryan.  But, because of its location in the air duct channel it does supply negative pressure to the crankcase.  Which is of benefit to the engine internals as described prior.

Southern California had horrendous air quality in the 60's and 70's  It's not paranoia if breathing is hazardous to your health.  Ergo the development of CARB  (California Air Resources Board). The Feds and EPA followed suit when other dense US cities had worsening smog problems.
Do note that PCV valves were part of automotive builds well before any EPA mandates.  The motorcycle industry lagged behind convention on engine breathers by about 10-15 years.

FYI:  The first US model CB550 (1974) had the recirculation breather incorporated as standard equipment.  Earlier CB500s did have that dump tube, though.  The SOHC4 line improved with each model year, imo.

Cheers,

[Stev-o]

Airbox parts are plentiful, nearly all the cafe guys take em off. 

This may have more parts than you need, but I'm sure you could sell what you dont want.
There is someone always looking for the airbox lid....


https://www.ebay.com/itm/Honda-CB550F-Supersport-1975-Airbox-Assembly-with-Boots/123568386887?hash=item1cc53ff347:g:n-kAAOSwXAxcJpiI

[bryanj]

Thanks TT, as you know the early 550(K 0,1,2) did not come to UK and the ones i have worked on have ended up with 500 airbox as that was all that was available over here. Since there is no longer surface mail from US to UK i rarely buy from US now due to carriage cost so buy far less from ebay for my projects.

[TwoTired]

I took the parts out of my 77 CB550 F.
Here are some measurements relating to the pics of parts you posted earlier.
Base width. - 2.864 "
base Length - 3.722"
Top Tube length - 1.169 "  Earlier models had a longer tube.
Tube outer diameter - 0.500"
Base "well" depth for foam element - 0.366"
This is base to crown top where tube is attached and gasket rests. 1.180"

The base gasket is a "U" channel type that captivates the perimeter of the base.  About 1/8 inch square end section material.

I took pics, but my phone won't talk to this computer.  I'll have to charge up the old camera batteries, and then post those pics later.

Cheers,

[58webbing]

Thank you for the dimensions I can now set about designing a suitable alternative. It will probably be a bit simpler than std to lend itself to the tooling I have available. I will upload info as I start to make progress.

As I live in the UK importing stuff is usually cost prohibitive, postage and customs charges can be horrendous also the couriers will always charge in excess of £10 on top and call it a handling charge! Free trade? I don't think so.
 
The additional info has also been usefull and, I think that as Honda owners we are fortunate in having a forum that has such a diverse knowledge base and interst in the detail.

[Deltarider]

I wonder if it had so much to do with air pollution. I'd expect it was more about getting rid of drips of oil spilled on the turmac (which the simple tubes do), not only polluting the environment but also creating a serious hazard, not at least for motorcyclists. To me the then new demand for motorcycles looks like a consequentional continuation of rules that already were there for trucks and cars.

[dave500]

ive got one of those new old stock here,still bright and shiny,it only serves to clog the airfilter like sniffing your own farts!a proper pcv valve system was never used on these engines,these were a half baked solution to satisfy smog rulings at the time full stop,its a crap set up.

[58webbing]

I have a plan. After studying the drawing and listening to the comments my conclusion is the Filter/Oil Separator is very un Honda like. It looks like the Honda engineers had only a few minutes to sort something out. The flow arrows are misleading as there cannot be a flow as such, because the engine is a sealed unit so apart from a bit of pulsing especially at low revs the only pressure can come from piston blow by.

The other anomaly as I see it is the air filter sits metal to metal on the "Element Cover" item 10 without a seal between the two (maybe to allow drainage) so the path of least resistance for the incoming air has to be through the resulting gap. Red arrows

The various differing views as to the effectivness of this device reinforces my un Honda like opinion.

What I propose to do is fabricate a box to sit in the bottom of the filter housing with a seal between the filter and the box, no tubes to the centre of the air filter. The drainage pipe item 6 will have a valve at the bottom not unlike the valves found on dirt bikes, to let stuff out but not in.

The theory is that air bourne pollutants will be drawn up into the engine while the heavier pollutants will let gravity take them to the drain pipe. Also the engine internals will be under a slight vacuum which should be better than the dubious venturi effect of the current setup. All that remains is to make something and try it out.

[TwoTired]

Be aware that your diagram doesn't show that the stock drain pipe tube had a cap at it's end with a slit in it,  Called a pinch tube, in operators manuals.  This will allow collected water to slowly drip out, but not allow air ingress.  At service intervals the tube cap is pinched, in case there is any sludge build up sealing the slit.  The arrows show the only path available for crankcase gases to flow in the properly operating system. Possibly it was originally made to show import officials how the crankcase hydrocarbons could not escape to the atmosphere.
The recirculator is essentially a closed system where crankcase vapors or gasses can only go to the filter box, as that is where the negative pressure is, relative to the filter box air entrance.  With the engine running, there is some negative pressure there.  And the smaller the air entrance opening, the higher the pressure difference.  The pressure difference is greater with, air velocity, too.  That's the nature of ductwork.  The pressure is always trying to equalize between the source of negative at the intake valve (falling piston), to the positive, outside air inlet.
Because the air box is sealed to the outside, a seal is not strictly necessary.  The rubber at the bottom of the steel tube assembly behaves as a cushion, and to keep metal to metal parts from worrying against each other.

The later CB750s had a recirculator, too.  Also a closed system, but with a very different physical arrangement. So, I don't agree with your assertion that Honda engineers did this as an afterthought. No SOHC4 had a flow through system such as those with PCV valves. I question if, due to the intake pulsing, whether a PCV valve could ever function properly. Still, the Honda system effectively routes hydrocarbons and water vapors into the combustion chambers, instead of into the air supply we breathe, at the same time it applies a small amount of negative pressure to the crankcase.  I thought it was quite clever, even if more complex in parts count and arrangement.

Do you still want pictures?

Cheers,

[58webbing]

I now have pictures of the various parts thank you

[Deltarider]

I now have pictures of the various parts thank you

You may find this manual by Sohron informative, say from p 65 on: https://drive.google.com/file/d/0B4nqeBb662mZMkxxdmVoWi1IMzg/view The original thread is here: http://forums.sohc4.net/index.php/topic,151576.0.html
If you really must, you can fit it, but you have to monitor it closely! It was poorly designed. Realise that it passes condens and whenever your engine sneezes back, your airfilter gets wettened. I've heard of people that turned to inferior foam filters because of this.

[58webbing]

Job Done. After much consideration the mk2 is finished. Its as simple as I could make it and should be easy to adjust and maintain. The unit rests on a foam seal and, the filter rests on a foam washer. The hollow body can be fitted with foam filters, if needed.

[bryanj]

Nice tidy solution, don't forget to clean out and/or replace the bit of foam (filter) occasionally as when it gets all crodged(technical term) up strange faults occur

[RAFster122s]

Where would you find appropriate foam for the filter?
David

[58webbing]

As an avid bin diver and hoarder of all things potentially usefull I would use this as a source and select what grade by experimentation. My theory is that the foam is just a barrier to help prevent any "Gloop" from entering the air filter proper. In an effort to prevent this I have deliberatly left out the bottom part of the separator as the intake holes on the original are very close to the bottom of the housing, the best place to suck up any "oily porridge"
What I am hoping for is for the device to maintain a vacuum on the engine, suck any vapours into the inlet and allow the liquids to drain out of the bottom, for this to happen on my design I dont see the need for any foam filter. Time will tell.
On other engine setups I have encountered the engine breathers were straight into the inlet tract no valves or filters. Problems occured when the pipes fell off, came loose or cracked, not too common a fault and an easy fix.
My nest task is to source some 12mm ID rubber drain valves, duckbill valves, reed valves or what ever.

[bryanj]

Seems standard in the UK to get one of the foam small square pan scourers and remove the abrasive part.

[Deltarider]

On other engine setups I have encountered the engine breathers were straight into the inlet tract no valves or filters.

I wonder what the back of their inlet valves have looked like...

[RAFster122s]

Could a 1/2"/13mm ball valve do what you want? 3d printed if you cannot find a plastic one might work if it is to regulate vacuum.

[58webbing]

I have been considering making a valve by fabricating a form tool and dipping it in a plastic coating, similar to the stuff used to make tool handles. Finding something soft and flexible might prove challenging.