Fuel puking out overflow line
 

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.

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

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.

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.

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. ;)

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

http://i729.photobucket.com/albums/w...r/oil_sep2.jpg

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.

The oil separator for the RX3 engine is shown below.

http://californiascooterco.com/blog/...1_4723-650.jpg

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

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. :tup:

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. :tup:

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.

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. ;)

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

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

vent hose
 

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.

Vent tube drips and oil leak
 

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.

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?

I don't think we have a good idea yet why some bikes are collecting "gas" (probably condensed unburned gas) in the vent drain tube. I don't think valve adjustment settings should be a factor, but who knows?

I had some problem with this, though not as bad as detours describes. I moved the vent line that runs past the cylinder up and out of the "holder" fitting, and also changed the ziptie that holds a bunch of the lines together a few inches back from the cylinder. I suspected that the holder/zip tie might be too tight, constricting the vent line that runs back to the airbox. Since I did this, I have had no further problem with "gas" dripping out the vent tube drain. But I am not convinced I have really "fixed" it.

Detours might try these simple changes and see if it makes any difference.

Thanks for the idea, nova. I'll check the airbox vent line.

Adjusting the valves will not affect the crankcase venting system.

Since the crankcase venting system is only connected to the crankcase and the air box, any fluid collecting in the drain tube must come from the crankcase.

Was your fuel mileage affected? Do you suspect you might be having problems with the fuel injector? :shrug:

The air box only provides enough negative air pressure to collect fumes from the crankcase venting system. Any liquids expelled into the crankcase vent system will collect in the overflow tube. It is difficult to believe that gasoline could be expelled in large quantities from the crankcase without either engine problems or reduced fuel mileage. :shrug:

So I'm still getting a lot of gas in that tube. The plug doesn't seal very well, but it still gets full despite dripping out. And whatever contaminants are in there, the liquid looks and smells just like gasoline. It isn't milky, sooty or dark and no particulates are visible.

Anyway, I followed NovaRider's advice and chased the hose back to the airbox. I found a little crimping at the metal frame clamp, but not too bad. I loosened it anyway. The zip ties were fine ... one loose and the other barely snug ... so I left them alone.

I had kind of decided to live with this, but NovaRider pinged me about it and got me thinking again. So I'll probably open things up this weekend and check for obstructions in the separator, the hose and at the airbox. Might call CSC for advice too.

btw, the bike is running fine. I get 65-70 mpg all the time and still have more power than my wife's TU250x.

Thanks for posting the update. :) Please do let us know what you discover. ;)

I'm beginning to think this is normal for this layout.My bike does the same thing in all things you described.I guess in most PCV systems this is just ingested back into the intake tract.It just seems like a strange setup,I mean why not just run it like everybody else does.Not sure what the real advantage would be over the conventional PCV system.

I am very interested to know if this liquid is flammable. Can you collect some of the liquid in a metal can, and see if it ignites?

I can tell you that it is fuel that is in the line.
I'm thinking that it is coming coming from the crankcase side and not the air box side.Normal ? Probably.

I had liquid in my line, but only one time after a commute back from work. It was also most definitely fuel. I haven't found it again since and I have ridden the bike under almost the exact conditions on several occassions, which is full out on the freeway (80 indicated and about 8500rpm) for about 25 minutes in hot weather (90+). I only seem to get about 55mpg while doing this commute.

I'm just asking, have you tried to ignite it?

I am having a difficult time understanding how that much fuel can get past the piston rings, enter the crankcase, and exit the engine as fumes through the crankcase vent tube. :hmm: In addition, as all this is happening, the engine is running great, and the bike is getting excellent fuel mileage. :shrug:

All gases exiting the crankcase vent tube should be drawn into the air box. If fuel is collecting in the drain tube, there must be some kind of obstruction in the vent leading to the air box; that is the only possible explanation.

Disclaimer: please observe any applicable local ordinance, wear the appropriate safety gear, maintain a safe perimeter from said combustibles and have a reclamation plan for any unburned product. A catalytic converter of some fashion would also help the environment.

:p

Of course, I thought those precautions were understood. :)

:hehe:

I think the high RPM/low vacuum situation of hi-way speeds creates this fuel build up in the stand pipe.I Never notice it until hi speed running.
All quite normal for the design of the system on this high revver.
It only amounts to a few ounces so a non issue for effecting gas mileage.
At least that is my take on it.

Here's a pic of the liquid burning. I have no doubt it's gasoline, whatever other contaminants may exist in it. The liquid is clear amber, not milky, with no sediment or particulates.

I still have not found time to open the airbox and look for obstructions there or in the line. Hopefully I'll be able to this afternoon.

Sorry for the trouble your having but thats a cool picture.


/

You won't find an obstruction because it is operating as designed.

Thanks for checking, and taking the time to post the cool photo. ;)

The fuel is leaving the engine as fumes. There isn't enough pressure to force a liquid up the elevated crankcase vent. The oil separator is supposed to separate the lighter gasoline fumes from oil and other contaminants, and the gas fumes are supposed to be drawn into the air box. That is the design. :hmm:

http://i729.photobucket.com/albums/w...r/oil_sep2.jpg

Since fuel is collecting in the bottom tube, there must be either an obstruction in the partial vacuum line to the air box, or the oil separator is defective. :shrug:

I suggest you also examine the oil separator. In fact, I suggest you contact CSC and ask for a replacement oil separator.

Do you notice the fuel collecting only after longer stints at high engine rpms?

I definitely see more fuel collecting after long, high RPM runs. When I finished our 4 hour ride to Estes Park yesterday, the tube was full to the top. I think some fuel collects all the time and slowly drops out.

As I see it The separator does its job as described and allows vapors by into the air box until high RPM's.In that scenario Maybe that is why the stand pipe is there to collect the solids that accumulate at High RPM's.Without the liquid standpipe than the air box could become over saturated with raw fuel instead of vapors.We may be all overthinking this one.

You could look at it as spare bonus fuel. Handy when you run low. :D

I use my RX3 mostly for commuting and my freeway portion is at or near redline, but I haven't had the fuel issue that you have, Detours. Interesting problem.

Just now, while writing this reply, I thought back to when I first received mine and remembered noticing that the U shaped clamp (just above the clutch release lever) on the left side of the cylinder appeared to be bent too tight. Looked as if it was skwooshing (technical term) the hose quite a bit, so I dis-skwooshed it a little until I felt it wasn't pinching the hose but would still hold it snug.

Have you given that a look? I'd go take a picture but I just got out of the shower, it's 91F, and don't really feel like putting clothes on. Neighbors have kids, you know.

Still, if your oil is smelling of fuel, I think you have some other problem than just a breather/separator. Injector dribbling when the engine is off? Interesting.