Topic: breather tube help

[aglick87]

Like an idiot, I didn't take notes when I was taking the engine out of my 78 550k.   Now it's time to put the breather tubes back in their place, and I don't know where they go.  Here's the openings I have.  1.) One in the upper cylinder head cover. 2.) a second opening in the distribution box between the carbs and air filter box.  3.) a third on the bottom of the air filter box which has the foam peice/breather assembly above it.  4) and lastly another on the side of the air filter box with a 90 degree hose fitting on it.  Does anyone know the proper routing of these tubes?  Any insight is appreciated.  I also have a small diameter vent tube coming off of the set of carbs.  I assume this peice is to allow air out of the carbs as the bowls fill.  so, I figure this tube just vents into the ground with the overflow tubes?  thoughts?

[pmpski_1]

On my 74 550 #1 goes to #3. Not sure about the others. Maybe they have to do with later emissions controlled equipped bikes?

- Brian

[aglick87]

hmm, you could be right.  But honestly, I don't know that it would even reach down there.  I thinkthat it either goes to #2 or #4.   But I can see how you would think the bottom of the filter box.  I'll wait for some more input from other members before I make any connections. thanks

[aglick87]

I have a handle on most of the tubes at this point.  The cylinder head cover breather actually connected to the box that distributes the air to the 4 carbs.  The bottom nipple on the airbox vented to the ground.  now the only one I don't have an answer for is the one that comes off the side of the airbox with the 90 degree fitting.  so if anyone could help with that, I appreciate it.  and Justin, if you're reading this, do me a favor and take a look at your bike for me.  We have the exact same bike so that would make this easy.  Thanks all. 

[pmpski_1]

Cool...Glad you got it sorted out. I just got a copy of the factory shop manual and the '76 Addendum has a note that shows the breather tube from the cylinder head being re-routed out to the ground.

- Brian

[Kixx007]

On mine there is a tube that goes from the cover on top of the motor, to the bottom of the air box.  There is also a tube that vents to the atmosphere that comes off the bottom of the airbox.  There is then a third tube on the part of the airbox that connects to the carbs, that tube is vented to the atmosphere as well.  The small vent on the carbs, vents to the atmosphere also.  They all in some way, route down between the motor and swingarm.

[Justin_NJ]

I'll try to check that last connection for you tonight. 

Justin

[aglick87]

thanks for the posts guys to help me sort this thing out.  Kixx, I have a few questions for you.   If the breather from the top of the motor does in fact go to the airbox, which fitting does it connect to?  The one on the battery box side or the one that is pointed towards the ground.  Because I was almost certain that the tube coming from the motor was too large to fit either of these fittings and also too short to reach back to the rear part of the airbox assembly.  is there another hose that it couples to?  And justin, i'll check back later this evening and compare your information with what was given.  thanks

[Glenn Stauffer]

I'm pretty sure that it goes to the fitting near the battery box side.  The one pointed to the ground is for another hose that exits near where your carb overflow hoses exit.  This one allows any liquids that collect at the bottom of the airbox to drain to the ground.

--Glenn

[aglick87]

looking at the fiche on psp sparked another question.  the fuel tank breather.  wouldn't you want this tube connected to your intake somewhere.  say where the airbox connects to the carbs.  this would put excess fuel fumes where you want them, in your engine. 

[Justin_NJ]

I'm not saying this is correct, but this is how I have it:
- cylinder head tube goes to the bottom of airbox to the large-diameter 90-degree "elbow" connector
- the gas overflow tube vents to the air under the bike...in fact, so do all the other tubes on your list

[pmpski_1]

OK, I got this image from the PDFs at Honda4Fun. It shows some of the breather tubes and tells a little about why it's done this way. I know these are a little hard to read so I'll add what I can here:

1. Cylinder Head
2. Breather Tube
3. Carb
4. Air Cleaner Chamber
5. Element Seal Case
6. Drain Tube
7. Seal Plate
8. Punching Metal
9. Element B
10. Element Cover
11. Air Cleaner Element Spring

The paragraph below the photo goes on to say that the blow by gasoline from the cylinder head goes into the breather tube to the airbox. It passes through items 7 - 10 where the gas is separated from the oil. The gas then goes back into the carb to be re-used.

I know that when I removed my airbox (74 550), #6 above was routed out by the swingarm. However, it was capped so that nothing would actually drain.

If anything, hope the image helps

-Brian

[aglick87]

yep, I was out in my shop wrenchin on the bike tonight and that is exactly how it is supposed to go.  So, Justin, Glenn, and others were all right.  The cylinder head breather goes on the side of the airbox with the 90 degree fitting and everything else goes to atmosphere.  That includes the fuel tank, carb overflow tubes, carb bowl breather, battery overflow, breather on bottom of airbox, and distribution chamber breather.  Thanks everyone who gave their time to helping me figure this out.  The nicest people on earth really do ride a honda.    peace

[billstron]

I am activating an old thread because of the picture.  I have a '78 550, and I have some questions about where breather tubes rout.  On mine, there is an opening in the bottom of the air box like the cylinder above the #5 in the picture.  What connects here?  The PO had the head breather tube connected here, but after reading some more, I think that needs to be connected to the bottom of the air filter. 

I am trying to cure an intermittent smoke problem out of #1 and 2.  Since I am not filtering the breather suck through, I have been wondering if the smoke could be produced by oil coming in through the intake from the breather. 

What do you think about the hose routing etc. 

Thanks...

[TwoTired]

I am activating an old thread because of the picture.  I have a '78 550, and I have some questions about where breather tubes rout.  On mine, there is an opening in the bottom of the air box like the cylinder above the #5 in the picture.  What connects here?  The PO had the head breather tube connected here, but after reading some more, I think that needs to be connected to the bottom of the air filter. 

The nipple at the bottom of #4 is an emergency drain in the event the fuel in the carbs over flow.  Not and engine breather connection.  The Honda supplied hose that installed there was a reduced diameter type that simply routed to the bottom of the bike between transmission case and swing arm.  It always bothered me that this was a filter bypass in a high suction area.  But, at least the stock tube had a very small diameter at the end.

The diagram posted above from the Honda shop manual clearly shows the engine breather coming from the top of the engine going to the side of the air filter box.

What is not shown in the picture above is that the tube installed at the bottom of the Air filter box (item #6) is supposed to have a cap with a slit in it.  This creates a pinch tube that you pinch to drain out collected condensation from the breather assembly when you service the breather filter element (#9).  The cap prevents air ingress during normal operations.

Cheers,

[billstron]

TT -- That is the perfect, and succinct, description I was looking for.  Thanks a ton. 

What do you think about my theory on why I'm smoking?  Am I smoking something? 

[TwoTired]

I think your theory has some merit. That air plenum drain IS on the 1/2 cylinder side ahead of the carbs.

Rather worrisome that enough oil is coming out the breather to show in the exhaust, though.

Is it only smoking at high RPM when the throttle is open?

Cheers,

[billstron]

It only smoke at idle, that I know of.  And it seems to smoke more if I've been flogging it a bit, especially if I use engine braking much. 

It also seems to smoke more if it is on the side stand. 

That help at all? 

[snoop]

I removed my breather element filter, could removing it cause smoking'?  what are the effects of not having it in? 

[TwoTired]

Starting to sound like valve guide seals. How many miles on the engine?

Have you done a compression check?  Wet/dry?

I have a theory that the 77- 78K models with their unique carbs and exhaust, and being the early emission test mules, ran hotter than the earlier models and cooked their valve guide seals faster because of it.

My 78 K smokes, too. I bought the guide seals but haven't put them in yet.  This bike has a very questionable maintenence and care history, too.  So, I could be living on hope, I suppose.

Cheers,

[billstron]

I too am living on hope because my bike also has questionable maintenance and repair history. 

I have done a dry compression test.  #1 had the highest compression at 175psi, and the other were around 130psi (I think).  It was a while ago, and I need to repeat the measurement to ensure its accuracy. 

It doesn't smoke that much, I am putting off any serious internal engine work. 

Oh... and I almost forgot.  It has 30k miles on it. 

[Chicago550]

Two tired do you happen to know where I can get that cap for the breather tube? I ordered a replacement tube from David Silver and noticed that the cap must be a separate piece (since it wasn't included).