Topic: Help with this piece on my engine...

[Foyil100]

Hi All,

I removed my oil tank today in order to clean up my bike a little bit and I noticed this piece sticking out of the motor and I had no idea what it is...Can someone help me out? Should it just be as it is in the picture or is something supposed to be over it (a hose of some sort..?).

Thanks!

Sean

[BomberMann650]

It most certainly is a hose connection.

I'm not a 750 owner, but I'm fairly certain an oil hose belonged there

[flybox1]

That is the oil tank overflow tube.  If your oiling system gets backed up into your oil tank, it has to be safely routed back to the crankcase.  Get a hose on there asap.  It connects to the bottom of your oil tank.

[Foyil100]

Thank you! I had a local shop install a aftermarket oil tank on the bike (haven't started it or even filled it with oil yet) and I noticed one of the hoses went from the tank to under the bike..similar to a dirtbike fuel overflow hose that just hangs down. It definitely wasn't connected to the bike 

Good thing I asked! Thank you!!

[ekpent]

 That hose you described may be the aftermarket tanks vent and may possibly not want to be connected to that fitting. A stock honda tank has both an overflow and vent, your new one may not. Post a picture of it for the folks.

[Foyil100]

I'm using the Cognito Moto oil tank seen below and here: https://cognitomoto.com/products/bolt-on-cb750-oil-can

Its the smaller one on the far left.. The two large one connected to fittings on the bottom right side of the engine.

[Bankerdanny]

I think Fred is a fine name, Frederico if you want something more exotic.

[carnivorous chicken]

I think Fred is a fine name, Frederico if you want something more exotic.

Beat me to it, I was going to suggest "Terrence" or "Terry" for short.

[Foyil100]

Haha I see what you did there....

[Foyil100]

Does anything need to be attached to this piece or can I leave it the way it is?? I believe the third hose on my tank is a breather

[BomberMann650]

Does anything need to be attached to this piece or can I leave it the way it is?? I believe the third hose on my tank is a breather

That is the oil tank overflow tube.  If your oiling system gets backed up into your oil tank, it has to be safely routed back to the crankcase.  Get a hose on there asap.  It connects to the bottom of your oil tank.

What flybox said.

[Foyil100]

Here's the problem.. The oil tank (shown above) has 3 hoses, 2 run to the engine on the bottom righthand side and the third (smallest of the three) is a "breather hose" according to Devin at Cognito Moto (created of the tank). He said it can just hang down under the bike.

Should I connect that "breather" hose to that piece on the engine? Or should I plug that piece?

Thanks!

[Phinn]

Definitely connect it. If that rear-facing connector on the crankcase is left open, oil spits out the back and all over your rear wheel.  That's what my PO did, and because motorcycle oil leaks go everywhere, it's one of the sources of oil spatter that I've been cleaning off my bike since the day I got it.

[Foyil100]

Okay thanks for the info! My only concern is will it cause any problems having the "breather" hose connected to that?  I mean.. What is the breather hose used for? Is it bad for oil to go up there?

[Don R]

 Maybe run a hose up to a tee, connect to the top breather and then to a K&N breather or the airbox?  It should only pass air and  that would allow any oil venting out the top a chance to re enter the crankcase.
 A local shop had a 750 in with oil leaks everywhere, the PO had sealed the hose nipples with silicone. 

[Phinn]

Okay thanks for the info! My only concern is will it cause any problems having the "breather" hose connected to that?  I mean.. What is the breather hose used for? Is it bad for oil to go up there?

That's how the stock oil tank is configured -- two main in/out hoses, and one breather connection to that nipple on the lower rear crankcase.

There is a second breather on top of the engine, in the valve cover, which (on the 78s) connects to a separator that hangs below the battery box. It separates the output into liquid and gas, sending the liquid to a filter and then the street, and the gas back into the airbox. 

But the lower breather connector you've been asking about just goes to the oil tank.  These breather connections and hoses are there to deal with the expanding gases and occasional small quantities of overflow that occur due to heat and other operating conditions. 

[Foyil100]

Okay thanks for the info! My only concern is will it cause any problems having the "breather" hose connected to that?  I mean.. What is the breather hose used for? Is it bad for oil to go up there?

That's how the stock oil tank is configured -- two main in/out hoses, and one breather connection to that nipple on the lower rear crankcase.

There is a second breather on top of the engine, in the valve cover, which (on the 78s) connects to a separator that hangs below the battery box. It separates the output into liquid and gas, sending the liquid to a filter and then the street, and the gas back into the airbox. 

But the lower breather connector you've been asking about just goes to the oil tank.  These breather connections and hoses are there to deal with the expanding gases and occasional small quantities of overflow that occur due to heat and other operating conditions.

Thanks Phinn!

Okay so I'll connect the breather hose to that part of the engine. Therefore all 3 hoses will be plugged into the engine and no hoses will be hanging down. Mine is a 1978 CB750F Supersport, however I don't have any other hoses hanging down that might be a pure breather for gasses. I just want to make sure the bike will be able to release any gasses is needs to...