Oil smells like gas... By DrRocco (Read 12,275 times)

[DrRocco]

Just to make sure I understand what you're saying...

You think gas is getting in via the vac lines and there are two ways that could happen.
1: Via the vac hookup to the fuel shutoff.
and/or
2: Air cut valve diaphragm.

Correct? What's the air cut valve diaphragm?

[Alleyoop]

If this is a 50cc it does not have an ACV Valve on the throttle side it will most likly have a pump on the carb. If its a 150cc then yes it most likely will have a ACV Valve on the throttle side with a Vacuum hose going to it.

Now the other thing that will cause a little bit of gas to get into the oil is Hard starting. If you crank and crank before it starts where do you think that little bit of gas is going, YEP down into the crankcase.

So since you already checked the petcock take the vacuum hose at the INTAKE MANIFOLD and see if it is wet. If the Carb has an ACV valve disconnect it at the MANIFOLD or at the "Y" OR "T" connection.
Alleyoop
Here you can see where the ACV valve is on a carb:

[DrRocco]

Alley, it's a 150cc.  I'll take a look at what you suggest in the morning.

[Bashan]

Here is the deal, at #1 you see the vacuum fuel VALVE....not a pump...a valve. Bear with me, 150's usually do not have a pump which is much bigger. This valve is often mistakenly called a pump because when it is actuated by the vacuum of the engine gas spurts out of the line and it appears it is being pumped. It is simply gravity feed being rapidly opened and closed by the vacuum of the piston. I don't know about y'all but I have broke out in a sweat! The vacuum fuel valve can also manifest as a tank petcock. It is the same thing as the fuel valve except it hangs under the fuel tank and has a much more provocative name. Maybe Alley or JR can scrounge up a pic and help me out!. But the petcock does the same thing, the vac line pulls on a diaphragm and opens the valve:

Here's where the problem can arise, the rubber diaphragm between the two parts of the fuel valve can leak. It's actually kinda common. Gas then is pulled into the vac line and ends up, due to suction, in the intake manifold (#3). Is anybody else sweating!? Just me? OK...Sue, what is the thermostat on? On the wall.....that is just hilarious and Seinfeld is on the phone.

There can also be a vac actuated valve on the side of the carb. This is the air cut valve and through an unbelievably complex process involving cams, pushrods, cranks, and cranks changes the mixture. I am sorry, I am still sweating! SUE?! Oh, in your office and the lock is stuck....AGAIN!? Alright, I've been working out, I'll get the door open....give me a minute.

This valve cuts the air when you shut the throttle down. That makes the mixture richer and prevents backfiring from a rude lean mixture. Alley can explain this better as he is more rude, and just a little bit leaner than me. Is anybody sweating again? Good grief! The problem arises when the diaphragm leaks (snik) and gas is pulled down to the intake manifold, past the head, down the cylinder, past the connecting rod, past the crank, and into my favorite....the crank case...that's right ...the crank has a case. That was JR congratulating me on my award from the "12 year old's tech institute involving farts and belches". (12YOTIIFB)" Google it, I'm there...The Great Bashan

Thought I was done did you? No such luck! So what do you do? You run the bike a while. Then you pull the vac line off of the intake manifold nipple and smell for gas. No, I am not making these terms up, or the phraseology, and y'all need to join the vaunted 12YOTIIFB. The Great Bashan...now I'm done. Now PM me and tell me how weird I am....I love it. :-*Sue, that office door is commin' down, I'm a commin' for ya and I'm bringing hell with me! Ow! My hip! Give me a minute, the thermostat is stuck on the wall. It's not stuck on the wall it's, oh gaaahhhd! The Great Bashan

[kz1000st]

I think you guys are really over thinking this. What do you think used oil is going to smell like? Lavendar. He's new and very cautious. Especially the first sump he dumps. All kinds of crud in their. It's from China, they might clean parts with M.E.K. for all we know. Don't sweat it Doc. The engine will break in, all the mystery ailments will cure and you'll live happily, ever after. Don't look for trouble is my motto. Trouble finds you.

[twowheeler]

See! That old gas wanted out prety darn bad!

[Bashan]

Two T's TW.....hit it twice. Gaaahd! These kids! Pick up your socks too!

[dan50]

I can't believe you put 2 year old gas in a new engine. Gas with Ethanol (E-10) has a shelf life of 90 days. After that it separates. The Ethanol is crap for your engine and the gas has less that desirable octane. The Ethanol has octane, so they lower the octane rating of the gas they mix it with.

[Bashan]

Here is the air cut diaphragm:

I used to use clear lines for the vac system because you could see two things:

1. If the vac system is not leaking you will see a condensate appear as the vacuum increases due to the lower pressure. This always told me if I had leaks.

2. If I had gas getting into the vac system you could see it. I in fact had a rather bad air cut leak and gas was traveling down the ACV vac line.

I've heard people say gas in the oil is benign. It is NOT. Yeah, it's a petroleum product but it dramatically reduces the viscosity of the oil. It ain't very slippery either. Rich

[clonedrone]

Uhhmm, Ya ,What He said ^^

[tvnacman]

Gee using gasoline where you should use KY is not a good idea ?

John

[LUKE]

Mar 20, 2014 5:10:00 GMT -6 kz1000st said:

I think you guys are really over thinking this. What do you think used oil is going to smell like? Lavendar. He's new and very cautious. Especially the first sump he dumps. All kinds of crud in their. It's from China, they might clean parts with M.E.K. for all we know. Don't sweat it Doc. The engine will break in, all the mystery ailments will cure and you'll live happily, ever after. Don't look for trouble is my motto. Trouble finds you.

I totally agree, Rocco is just being paranoid, oil may definitely smell like gas because both are a derivative of petroleum. im amazed how this thread has fished out tons of responses but the fact maybe no real problem yet occured.
come to think of it, is there a way gas can get into the oil reservoir ? i dont think so, you might all be thinking that gas tank is above the engine and u therefore concluded that the culprit is gravity... so stupet!
the first sign of a troubled fuel line is gas dripping on the floor, and NOT oil smelling like gas, gizzzz!!!!
dont let Rocco fool us, the next time rocco cry for help, nobody will listen,, i forgot but there was a story about that, its like a parable of a crying boy. lol

[cyborg]

WHAT IS THAT???

[randy]

If I remember correctly you were heat cycling the scoot by letting it idle up to temp. and shutting it off and repeated this several times. I would just change the oil and ride the bike and monitor the oil. If the level comes up you have a problem but all oil is going to have a crankcase smell to some degree.But the level should not increase.

[Bashan]

Mar 18, 2014 11:02:06 GMT -6 DrRocco said:

I put the first 100 Km on my scooter and decided to do the first oil change.  A few days ago when I checked the oil, it was way over-full,

You guys are missing the point, it's not just a little blow by, it's actually filling the case up....THAT is a problem. IMOAISAHROTO (In my opinion and I'm sure as hell right on this one).