Fuel puking out overflow line

[NoVa Rider]

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.

[detours]

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

[SpudRider]

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?

[SpudRider]

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.

[detours]

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.

[SpudRider]

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

[Inroads]

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.

[SpudRider]

Originally Posted by detours

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...

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?

[Inroads]

Originally Posted by SpudRider

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.

[roots]

Originally Posted by Inroads

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.

[SpudRider]

Originally Posted by Inroads

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'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. In addition, as all this is happening, the engine is running great, and the bike is getting excellent fuel mileage.

[SpudRider]

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.

[Weldangrind]

Originally Posted by SpudRider

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?

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.

[SpudRider]

Originally Posted by Weldangrind

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.

Of course, I thought those precautions were understood.

[Inroads]

Originally Posted by SpudRider

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.

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.