Topic: Breather tube at the bottom of the oil tank?

[ron.cieri.313]

Hi all...ron here talking about his Honda CB750 K ('76)...which btw, has made real progress since the tranny is working and the stock air box has finally been installed....still have some idling probs by have been lessened (it cuts out if eventually and shuts down if left idling)

...but i digress, here's my question...is there a breather tube that sticks out of the bottom of the oil tank, about 1 1/2" long?  It was dripping a little bit of oil and can't remember seeing it before.  From the manual or the fiche I can't see anything exactly like it but from what i can see in the diagrams, I'm assuming its a breather tube...correct?  Does it need to be connected somewhere? or just connect a rubber hose and direct it off to the side?...thanks all, ron...

I do have a pick and will post later.

[MCRider]

It is there, and it should have a hose connecting it to the spigot coming off the back of the transmission. Please do this soon, as the tranny spigot can blow out oil onto your rear tire.

[ron.cieri.313]

oh my lord...the spigot right at the very back?...I have one end of a rubber hose connected to that that spigot an the other end just dangling down...cripes...so one end goes into the back of engine block (as i have it currently) and then the other end connects up into the breather tube from the oil tank so oil connected from the breather box gets transfered back into the tranny...correct?...thanks MC!

[MCRider]

oh my lord...the spigot right at the very back?...I have one end of a rubber hose connected to that that spigot an the other end just dangling down...cripes...so one end goes into the back of engine block (as i have it currently) and then the other end connects up into the breather tube from the oil tank so oil connected from the breather box gets transfered back into the tranny...correct?...thanks MC!

That's right, tranny to tank. A little explanation. The tranny breather is just that a breather. usually it should only have a slight mist coming out of it. But as i and many others here have recounted, if that is left open to the atmosphere and usually after a good hard run, it can puke quite a bit of oil onto the tire.

So, hook it up to that spigot on the lower backside of the tank. If you've had the chance to look into an empty tank, you can see that spigot entering the tank and continuing as a solid tube up the inside of the tank and terminating in the separator/condensor thingie at the top ot the tank. (Otherwise oil would come pouring out of that spigot full blast.) From there the tank vents to the atmosphere or to the airbox on later models.

[ron.cieri.313]

so cool...that is just what happend...after a real nice run I found oil on the floor and she hasn't been leaking a drop till then...i found the tank breather tube and it was wet with oil, I didn't check the other tube which could have been the source also...will hook up tonight!..thanks again and appreciate the explanation too.

My idling problem I should probably start another post...it's much better I keep her idling around 2000 rpms maybe 1900  but obviously not good enough.  I replaced the floats on two carbs with led to improvement.  I also have a "push" throttle cable issue so I waiting to replace that before attacking further...might replace the floats on the other carbs and then I think during the winter...I will pull the carbs and replace the needles inside...its definitely getting closer....she runs fine at low throttle now

[mystic_1]

The lower spigot on the oil tank is part of the oil-vapor separator on the tank.  The separator is a small canister inside the oil tank, vapors are separated from liquid oil here, the vapors exit the tank through the upper, larger hose.  The lower, smaller hose returns the liquid oil to the engine via the spigot on the back of the transmission.

Also, the automatic chain oiler seems to be fed by oil coming back into the motor via the aforementioned transmission spigot.  The catch tray that feeds oil down the final shaft is positioned directly under this spigot.

mystic_1

[ron.cieri.313]

Thx mystic...I turned that oiler "off" with some silicone goo as u know it makes quite a mess...I think you enlightened on the catch tray when I was rebuilding the tranny and some of you folks said don't bother when I noticed I didn't have one.

There is only one big spigot on the back of the tranny as I remember it...right?...it is parallel to the ground/horizontal, correct?...thx...ron.

[MCRider]

Thx mystic...I turned that oiler "off" with some silicone goo as u know it makes quite a mess...I think you enlightened on the catch tray when I was rebuilding the tranny and some of you folks said don't bother when I noticed I didn't have one.

There is only one big spigot on the back of the tranny as I remember it...right?...it is parallel to the ground/horizontal, correct?...thx...ron.

Mystic adds some good perspective. Sine the symptom of leaving the hose off is oil on the tire, I'd thought the maine direction of flow was from the tranny to the tank. But obviously the reverse is also true.

Leaving the catch tray out reduces oil to the oiler by quite a bit. Blocking the hole in the shaft is the final solution.

As to the spigot, or nipple in less elegant circles, yes there is only one, should be obvious.