Topic: What is this thing below my battery holder box???

[kjdelaney]

I have a 77 cb750k. What is this, and why is there, and what is missing???

[CycleRanger]

That looks like part of the PCV system. It should route from the crank case to the air box.
Check the parts list or shop manual.

You can get both here: http://honda.centralcluster.com/materiale-documentazione-tecnica/shop-manual

http://honda.centralcluster.com/materiale-documentazione-tecnica/parts-list/parts-list-cb750

 

[kjdelaney]

Was there a collection bottle or something there? My bike didn't have a stock air box  it. It came with PODS.

[TwoTired]

It's not really a PCV, as there is no Positive Crankcase Ventilation.  But, it does something similar by routing engine crankcase vapors (blowby, oil, and water) and routing them back to the engine to be burned instead of dumped in everyone's lungs.

It's certainly missing the hoses, and maybe the collection drain, and internal screens/filters to keep chunks from being ingested  by the engine.  The device benefits both engine and people when it's working, though some don't care about that.

You can see the other bits of it in this diagram:
http://www.cmsnl.com/honda-cb750k7-four-usa_model14395/partslist/F15.html

Cheers,

[Bonesaw]

You're missing most of it, its important for your engine, it separates oil and vapors, recirculates oil into the engine, and collects vapors into a tube for later disposal.

In that diagram, it's part 21. You won't be able to find the foam filter element anywhere, but you can cut a piece of green or blue scotch pad to fit in there and it will work fine.

[kjdelaney]

Ok. So the crankcase breaths into that bottle and the bottle filters it back into the air box. If it is necessary then how do i run this system with out the stock air box?

[Tree]

I've been told it will function normally without it. I don't think these recovery systems existed prior to '77.  Need to add a small filter of some kind on the breather tube coming off the top of the engine (where the hose use to connect) so that it doesn't ingest something.

[Bodi]

It is not necessary. You reduce pollution slightly by using it: the crankcase gases contain unburnt fuel and oil vapor. It's not a huge amount and lots of older engines just vent this stuff. The "recycling" system came in mid-70s with tighter vehicle pollution regulations. I don't think you will run into any legal problems if you don't have it working.
You can just run the vent tube down below the engine with the others, but it's a fair idea to add some sort of filter to keep dirt and bugs out plus you can have problems if the crankcase vent  gets clogged or plugged with dirt. or bug cocoons.  There are "mini-pods" available for just this purpose.

[stinkfinger]

Mine isnt hooked up either as im still missin some parts also.
I have the hose from the top of the motor over to the collection thingy,
but not the bottom thingy and hose back.
It smokes/vapors a little when the bike is up to temp.
Post pics/sources if you get the rest of your stuff, thanx

Tony

[stinkfinger]

There are "mini-pods" available for just this purpose.

Sounds good too

Tony

[Hinomaru]

When running pods, attach a vent hose to the valve cover and route it downward as shown below. The KO thru K6 bikes used this same setup from the factory. The open end of the hose should be kept at least two inches away from the rear tire.

(Pic is vent hose routing taken from a 750 K6 model)   

[kjdelaney]

When running pods, attach a vent hose to the valve cover and route it downward as shown below. The KO thru K6 bikes used this same setup from the factory. The open end of the hose should be kept at least two inches away from the rear tire.

(Pic is vent hose routing taken from a 750 K6 model)   

I have a valve cover vent like that but it wasn't that long. I'm going to cut off "the hangy thing" and just run the vent with the others! Thanks for all the help!