Fuel puking out overflow line

[Inroads]

Anyone else have this going on ? I just got thru with a 50 mile high speed run and my clear overflow tube on the left lower side of the bike was full of fuel.
I wonder if I'm beginning the injector symptoms that "at wits end" is having ?
My bike is running great after adjusting the valves,with no stumble or dying issues.I will now be pulling the air cleaner out to see what it looks like.Also I'm going to monitor my gas mileage.
I do not appear to have a rising oil level like the other guy here has.
I'll report my findings.

BTW,for anyone having issues or questions about our bike(since we're the North American guinea pigs)
Now would be a good time to ask Joe at CSC because he and those Zongshin engineers are blasting
the West on a 2 week road trip.I'll bet they would have some insight.

[rjmorel]

Mine would get 1-2" in the tube when I first got it. CSC told me to leave the plug out and let it do it's job and drain. Doesn't indicate a problem just that it is venting and sucking stuff out of the system just like a car pvc does. I compromised and drilled a 1/16" drain hole in the plug and never think about it anymore. rj

[Inroads]

Problem is my 6" tube was full of fuel after a 50 mile hiway run.
On the return trip a tad slower(65-70 indicated) and about 1/2 full of fuel.
Where is the fuel coming from ?
There 2 lines that dump into that overflow line 1 comes from the airbox and the 2nd
Comes from the crankcase.
I drained my oil and I have no fuel in my oil and so I was thinking that it would have to be coming from the bottom of the airbox,I pull the filter out and it looks perfect along with the bottom of the airbox....so where in the heck is ithe fuel coming from ? Beats me.
Also I have developed an oil leak that was enough to cause oil dripping off the left case covers and onto my shoe.

[3banger]

I have noticed this as well and it is most certainly fuel collecting in this line.

The Evidence so far is:
I did not note any liquids collecting in this line until I dressed up the plastic plug with a little bit of sand paper and made sure the spring clamp seal the plug in the tube with a bit of silicone grease. I suspected fluids where just leaking past the plug.
The liquid that collects is too thin to be oil and smells of gasoline.
While adjusting my valves I pulled pill shaped separator. The inside of the hose running back to the crankcase appeared dry as was the hose running to the air box. The inside of the air box was dry. The separator is filled with a coalescing media (foam).
Oil level is remaining constant.
No soot is collecting the tip of the tail pipe.
Bike has 600 miles as of today.

From this I Conclude:
Some amount of gasoline is making its way past the rings and into the crankcase either as liquid or a vapor. It is vaporizing out of the oil and going out the crank case breather then condensing in to coalescing media and collecting in the catch tube. My bike has been doing this from day one but I didn't notice until I sealed the plug fitting in the tube. This also explains why some are seeing this and others aren't; some of the plastic plugs just happen to make a better seal.

Additional Hypothesis:
All of the bikes I've owned so far have the crank case vent tubed directly to the air box with out any type of separator device. I suspect we would see this on all engines to some degree if we added this component.

[SpudRider]

Here is the short answer; I will post a more detailed answer later, along with a diagram.

The Zongshen RX3 employs an oil separator in the crankcase vent tube, which is the same design employed by my Honda XR650L motorcycle. The difference in the two designs is that the oil separator for the XR650L allows the liquid collected from the oil separator to be sent back to the crankcase, and the oil separator for the RX3 collects the liquid in the descending tube.

Some combustion gas, along with a trace of fuel, always gets past the piston rings and enters the crankcase; that is why every crankcase has a vent. Most engines vent this contaminated vapor either directly to the ground, or to the airbox, where the contaminated mist is introduced to the fuel/air mixture which is burned in the combustion chamber.

Some owners of the XR650L remove the oil separator, extend the vent hose to a higher location, and close the end of the vent hose with a small air filter. These filters always accumulate a collection of contamined goop which has been expelled by the vent hose, so the filter must be replaced periodically. The stock oil separator of the XR650L merely returns the collected oil, and the contaminants, back to the oil in the crankcase.

The contaminants collected in the downward vent tube of the RX3 will contain a little gaseoline. However, this contaminated liquid is normal, and it is not pure fuel. Instead of returning this contaminated liquid to the crankcase, the RX3 is designed for you to collect it, and dispose of it as you would with used motor oil.

If you fill the crankcase with too much oil, you will also find oil in the vent tube, along with the contaminated liquid with contains fuel/goop from the combustion process. If you don't overfill your engine oil, you will just get the contaminated liquid, which contains a trace amount of fuel which escaped past the piston rings.

If you get concentrated fuel in this collection tube, the fuel injector is probably dumping extra fuel into combustion chamber, which is leaking past the piston rings, and ending up in the descending vent tube. However, if the collected liquid merely smells a little bit like fuel, this is normal, and you should not be concerned.

[SpudRider]

The oil separator for the Honda XR650L is connected in the following manner.



The Honda engineers designed the crankcase breather as a closed system which vents into the air box behind the air filter. This location places the vent in an area of high air flow, which draws vapors containing contaminants out of the crankcase. Contaminated vapors are present because the piston rings do not seal one hundred percent, and combustion gasses sneak by the piston rings. The oil separator collects the oil and liquid contaminants from the crankcase gases, and allows the recaptured liquid to re-enter the crankcase. The contaminated gases are inserted into the fuel/air mixture, and burned in the combustion process.

[SpudRider]

The oil separator for the RX3 engine is shown below.



As the piston is pushed down by the burning fuel in the combustion chamber, some of the exhaust gas pushes past the piston rings, and exits the crankcase vent tube. This gas is also persuaded to exit the crankcase by the tube which connects the oil separator to the air box, which is an area of high air flow.

The crankase vent tube connects to the oil separator, which uses foam to separate the oil and liquid contaminants from the gas. Gravity causes the oil and contaminated liquid to fall into the tube below the oil separator. The contaminated gases are drawn into the air box, where they are infused with the fuel/air mixture, and burned in the combustion chamber of the engine.

The CSC blog describes this process in the July 1, 2015 installment, which is linked below.

http://californiascooterco.com/blog/?p=17262

[SpudRider]

The crankcase vent of every engine will expel a contaminated liquid which is milky white. If the engine oil is overfilled, the contaminated liquid will also contain motor oil. Some crankcase vents send both the contaminated liquid, and the contaminated gas to the air box. Other crankcase vents expel the contaminated liquid, and the contaminated gas to the outside environment.

The Honda and Zongshen designs are superior, since they separate the contaminated liquid from the contaminated gas. This keeps the oil and contaminated liquid out of the air box, and out of the fuel/air mixture heading for the combustion chamber.

Unlike the Honda design, the Zongshen oil separator also keeps the contaminated liquid from being sent back to the crankcase. Therefore, the Zongshen oil separator helps to keep the motor oil clean from contaminants.

[SpudRider]

I suggest you keep the plug in the bottom tube of the oil separator assembly. The plug helps to keep dust from being sucked into the foam of the oil separator, which will shorten its life. The plug also helps to prevent dust from being sucked into the crankcase itself. Also, if the running engine is submerged on its left side, the plug will help to keep water from being sucked into the crankcase. This is why most crankcase vent tubes terminate in the air box. The air box is a dust free environment. Also, if the bike is submerged, the vent is located higher, and is hopefully located above the water line. Finally, if the plug is water tight, the plugged tube allows you to collect the contaminated liquid for proper disposal, along with your used engine oil, instead of spreading the contaminated liquid into the environment.

[SpudRider]

Originally Posted by Inroads

...Also I have developed an oil leak that was enough to cause oil dripping off the left case covers and onto my shoe.

I suspect oil/grease is being thrown off the drive chain. The oil/grease strikes the stator cover, and drips down.

If you want to test my theory, clean the oil from the case covers with brake cleaner, and hose them off. Then clean the drive chain, but don't lubricate it. Finally, go for an extended ride, or several short rides. If the oil leak disappears after this experiment, you can be pretty confident the excess oil was being thrown from the drive chain.

[detours]

Thank you for that excellent description of how our PCV system works.

[SpudRider]

You're welcome. Thank you for your kind words.

[fishman10]

Spud is correct,,while early on csc was saying you could leave the plug out of the bottom of the vent hose,,,Jerry (csc tech) has informed me that was incorrect and the plug should stay in ,,for the reasons spud stated.

[NoVa Rider]

I'm having similar problems to Inroad.

After a longer freeway run, several tablespoons of "gas" drip out of my vent tube. Initially I also thought my oil level was rising, but now that I follow the recommended procedure for checking oil, I no longer think that is the case. And I no longer think its an injector problem, since the bike is running well. I now presume that the "gas" is unburned petroleum condensation that should have been run back to the airbox, but instead is collecting in the vent tube. While this may not be harmful, its not environmentally friendly and not so great for asphalt surfaces. I hope CSC and/or Zongshen come up with a remedy. I plan to take a look at the "hangers" that guide the black air tube from the separator along side the motor up to the airbox. Looks to me like they may be pinching the tube, which might block flow of crankcase fumes. Just a theory to look at.

And like Inroad, I am getting a film of oil on the engine, in my case mostly on the right side. I think its coming from a bolt or other fitting on the cylinder head -- I don't think is coming from the valve adjustment covers. I plan to pull the tank in the near future and see if I can find the source.

So far, I consider these teething problems. We're pioneers, after all.

[detours]

On my long ride through Poudre Canyon yesterday, my drain tube filled up and leaked at every stop. It smells very strongly of gasoline and looks like gas too.

It was always dry till I adjusted my valves. Could I have set them too loose? Or does that have nothing to do with this vent line?