fuel pushed through valve cover breather

[yentera]

Hello everyone,

I've got a 1980 gs750 that I recently bought. My issue is that it runs, but after a few short minutes fuel pours through the valve cover breather into the air box. There is an aftermarket pet cock put on after the original. I've heard that if the original is bad, that could cause the problem (vacuum issue). I'm wondering if you guys can either confirm or throw out other ideas. Thank you in advance.

[Who Dat?]

Sounds like something is DEFINITELY connected incorrectly there. That breather hose should connect only from the top of the valve cover breather to the top of the air box. If you have fuel pouring out from there, that would mean that your whole engine is full of fuel.

Open the oil filler cap on the clutch housing, smell the oil. If it smells like gas, drain the oil and replace it with fresh oil.

Check all your hoses to make sure they are connected to the proper places:
- the petcock has two hoses, a larger one and a smaller one. The larger one is the fuel supply to the carbs, it connects to the "T" between carbs 2 and 3. The smaller one is the vacuum hose, it connects to a nipple on top of the engine side of carb #2.
- there should be hoses on two "T"s that are between carbs 1 & 2, and 3 & 4. Those should be routed over the top of the airbox, and hang behind the airbox or lay on top of the air filter, under the seat. They are vent hoses and do not get connected to anything.
- there is one more hose that connects to the safety drain funnel on the fuel sending unit on the underside of the gas tank. That should be routed over the airbox, behind the engine, and be routed down below the swingarm. It is there to keep fuel off the hot engine in the event that the gasket on the fuel sending unit leaks.

Please check your hoses and report your findings.

[Guest]

Sounds like something is DEFINITELY connected incorrectly there. That breather hose should connect only from the top of the valve cover breather to the top of the air box. If you have fuel pouring out from there, that would mean that your whole engine is full of fuel.

Open the oil filler cap on the clutch housing, smell the oil. If it smells like gas, drain the oil and replace it with fresh oil.

Check all your hoses to make sure they are connected to the proper places:
- the petcock has two hoses, a larger one and a smaller one. The larger one is the fuel supply to the carbs, it connects to the "T" between carbs 2 and 3. The smaller one is the vacuum hose, it connects to a nipple on top of the engine side of carb #2.
- there should be hoses on two "T"s that are between carbs 1 & 2, and 3 & 4. Those should be routed over the top of the airbox, and hang behind the airbox or lay on top of the air filter, under the seat. They are vent hoses and do not get connected to anything.
- there is one more hose that connects to the safety drain funnel on the fuel sending unit on the underside of the gas tank. That should be routed over the airbox, behind the engine, and be routed down below the swingarm. It is there to keep fuel off the hot engine in the event that the gasket on the fuel sending unit leaks.

Please check your hoses and report your findings.

He has another post on this, pretty much told him do not ride the bike until you got this figured out.

[tom203]

"There is an aftermarket pet cock put on after the original."

after you figure out which hose goes where, be suspicious of the petcock, so test it.

[yentera]

Screenshot_2016-02-03-09-44-25.jpg ok, proof that it is coming from the valve cover breather. Is it possible that one or more floats are sticking and flooding the crankcase, causing high oil pressure this pushing oil fuel mixture out of said breather?

[tom203]

Sure it's possible, but start by checking petcock for correct operation to rule it out as a problem. What is this "aftermarket petcock" ? Is it the leverless 1980 version ?

[tkent02]

Have you done any of the things such as seeing if the oil has gasoline in it? Checked the petcock? Checked the hose connections?

[Guest]

I'm sorry, but if you keep running it like that, you will deserve what happens.

[tkent02]

Boom !!!

[hannibal]

I can't seem to understand how the bike even runs. It can't last long in that condition. As folks have said, check petcock, needle vavles and seats, and floats.

[Guest]

[ATTACH=CONFIG]44021[/ATTACH] ok, proof that it is coming from the valve cover breather. Is it possible that one or more floats are sticking and flooding the crankcase, causing high oil pressure this pushing oil fuel mixture out of said breather?

Have you got back to your other post about this?

[Guest]

I know this post is dated, but I had a like issue. It was crazy watching black oily gass blowing out of the air box. I was totally baffled and distraught. Nothing this post. A petcock change and oil change. It came alive and runs beautiful. Thanks to those that posted.