Topic: 77' CB750 F Model Breather Separator Element

[BillyT]

I'm missing the foam element to my breather separator. Anyone know where I can get one or if there is a replacement I could find around the house? Would foam off a bed roll do the trick? 

 

[Wobbly]

Any piece of foam cut into shape will do just fine. Perhaps something used in packaging might have the right thickness. All it does is to absorb the little bit of oil coming its way so it doesn't end up in the environment. A sweating head gasket will produce more pollution though.
The actual part is no longer available from Honda.

[BillyT]

Thanks for answering! So close to getting the bike started!

[TwoTired]

You need open cell foam, that is fuel and oil resistant.

Closed cell foam will block air passage, defeating operation.  Some foam types will dissolve in a gas or oil vapors.  This make them collapse and block airflow. (And makes a sticky mess.)

[Wobbly]

TwoTired is right. If you want to put it in there and forget about it completely, you need to have the appropriate foam. What will work best is the foam used as air filter (in certain Hondas for instance). If you can find an old filter, it be perfect to cut out a piece. In the meantime, your Honda doesn't care if there is a filter in there or not. In fact, I have seen a lot of older Fours, where everything below the top cap part was missing without that anybody would have noticed.

[TwoTired]

In the meantime, your Honda doesn't care if there is a filter in there or not.

If you mean, as it runs today, at this moment, yes.  However, the breather does help keep the oil clean and also helps evacuate internal condensation.  So, long term, it is better to have the breather working.

There is also the breathing mammals concern.  You know, dumping piston blow by and hydrocarbon vapors into the air for everyone to breathe.  Carcinogens, asthma inflamation, emphysema etc. 

    

[flybox1]

Dont worry TT, the amount of Fukushima fallout Pacific mammals are, and will be exposed to will be worse than a lifetime of breather blow-by   

http://www.themindunleashed.org/2013/08/at-very-least-your-days-of-eating.html

[TwoTired]

In for a penny, in for a pound, eh?

If humans are the best this earth can produce... it kinda makes one wonder.

[Killer Canary]

You've just started wondering now?

[SohRon]

Dont worry TT, the amount of Fukushima fallout Pacific mammals are, and will be exposed to will be worse than a lifetime of breather blow-by

When the fallout starts looking like this we're in trouble.

Lots of younger guys have grown up after things like the breather system were invented and can't relate to the world as it once was, so they think this stuff isn't important. I was there... you need to use the breather system as it was designed. It will be better for your bike, and for your breath!

[BillyT]

TT, I am fairly certain the foam that I used is open celled but how can I be sure it will stand up to long term oil and gas contact?  Also, how thin do you guys recommend I trim the piece.  It's about 5/8" currently. 

[TwoTired]

If you can blow though it, it is open cell.
Unless where you bought it says what the material is, the only way to know is to test it.  Put a piece in a small jar of gasoline.  If it is still intact after a month, call it good to go!

[Wobbly]

Billy, I believe it is thinner than that. The separator still has to fit on top of it. But basically, if you fit it flush with the separator, you are good. Take a look at the Air Cleaner schematic to get a better idea: http://www.cmsnl.com/honda-cb750k7-four-usa_model14395/partslist/F15.html#results
Just to clarify: I am all for using the filter. But I don't think it makes any measurable difference one way or the other. My point was: don't let it sit in the garage because it lacks the little foam pad. And: most people don't even know it exists.

[Wobbly]

You want to see smog this is my next project!

Yeah, I would hate to drive behind you. But what project? It looks pretty good as is.

[BillyT]

Trimmed it down to about 3/8" as I guessed from that picture.  Also, I was waiting for the new oil filter and air filter to arrive before starting the engine.  Maybe I could go ahead and try to start it. But it hasn't been started in about 23 years and  the brakes and clutch need to be fixed.  It would be cool to start but I put so much work into restoring the engine I'm hesitant doing it without the new filters.

[Don R]

I used scotchbrite pads, a couple layers thick. Jeesh, this inocent Question took a twist.

[madmtnmotors]

I use the green foam air filter element for the little Briggs lawn mowers. Just cut a piece off the big end to fit the cup.

[Don R]

I use the green foam air filter element for the little Briggs lawn mowers. Just cut a piece off the big end to fit the cup.

There you go. Thanks from me too.

[madmtnmotors]

You're quite welcome. I remember this being a headslap moment for me when I thought of it way back when. Cheap and readily available too! 

Part of my regular maintenance routine now.

[Jonm99]

I received the filter element with the bike but it was never assembled. Does anyone have a diagram (or just an explanation) of how to install it? What connects to what? It's difficult (for me) to understand from the schematic alone. Attaching a pic for reference...

Thanks

[ZingZing]

I received the filter element with the bike but it was never assembled. Does anyone have a diagram (or just an explanation) of how to install it? What connects to what? It's difficult (for me) to understand from the schematic alone. Attaching a pic for reference...

Thanks

I'm trying to figure this out too. According to other posts I think the top goes to tube on the top of airbox, bottom is the drain tube (leave open or plug and dump), and the middle goes to valve cover breather. Autozone also has some foam designed for PCV and emission systems for $2 so I'll replace the breather element with that.