fuel in the oil issue/question

[ViperRon]

cavitation!!!!

Ok I have not had a motorcycle have a bearing fail from gas but my brother’s car, a 225 dodge slant 6 engine, had the fuel pump leak gas into the engine and it destroyed the bearings and crank. This happened within the time of an oil change, less than 3000 miles, because I changed the oil. I posted a reply above that explains that the problem has little or nothing to do with the gas thinning the oil. It has nothing to do with the solvent capability eating up the bearings. It has to do with the vaporizing gas causing cavitation.

I do agree that smell is not an exact way to check for fuel in oil because petroleum is petroleum and some can not tell a difference. I also agree that after oil has been run it has carbonized gas particles in it and any un-burnt residue from the cylinders that is not scraped off by the compression rings is circulated into the oil threw the oil rings.


All I can say is for those that really can not understand to do a little test. Take a milk jug with one of those pop off tops and put a quart of oil in the jug and shake it. Hey its still oil.

Now put 2 tablespoons of gas in it and put the top back on and shake it and see if it does not foam.


Now if you are really persistent and can not understand put 2 more tablespoons in it put the top on and shake it near an open flame and you will begin to see the light or at least this argument is over. Now this will not only prove out Newton’s laws of physics but also Darwin's theory as well. Your bike will also be here runing long after you have turned to ash and blown away.

[Bonz]

I have learned something about vaporization causing oil to cavitate, that is really interesting to me as I was of the knowledge it's the oil thinning out that is the problem. Makes perfect sense though, as gasoline has oxygen in it, you vaporize it and you create oxygen which will cause bubbles.

Still, I am checking into how much gas becomes a really bad thing in the context of our discussion, and hope to have some info to share.

Good discussion guys!

[jetmechmarty]

I just had my bike flood in the garage since I left home. Brent was kind enough to run up there and take care of it. According to his report there was no gasoline in the oil. In other words the oil level was the same as when I left it, and he said he couldn't smell any evidence in there.

I think the carburetors leak into the airbox first. I'm watching this thread as my oil only has 100 miles on it.

[BA80]

Another oil thread.


Simple answer.........gasoline in the oil is a bad thing for the reason of whoevers explanation you want to listen to.

[Bonz]

I second that. Another question now arises... It would seem if the engine is running, the engine is much more likely to fill up on fuel than if it is sitting in the garage, would that be correct?

Wouldn't the resepective fuel level needed to come out the airbox come into play first when the bike is level on the centerstand or on the sidestand? I only ask that because I have had flooded airboxes after sitting due to stuck needles/floats but have not seen higher crankcase levels at the same time as the airbox flood.

Looking back, I see mostly posts of "Help! Fuel came out my airbox..."

Has anyone had their airbox burp lots of fuel, AND had an overly full crankcase at the same time after the bike sat?

Just askin'...

[ViperRon]

I had a friend that had continual problems with the floats leaking on his and the cure was to put the bike on the centerstand and use a jack to raise the front of bike up till the rear wheel was on the floor. That way the gas is sure to run to the airbox lesser of evils. As it happened when he did this it never once leaked, the few times it did he had it on the side stand. He also liked to let it sit and idle and idle and idle on the side stand which I actually believe caused part of the problem.

Gas will not collect and run into oil while the bike is running excessive gas is sucked in the engine and blown out too much and it will quit from fouled plugs.

[Bonz]

My first fuel leakage occured when it turned out my needle seat o-ring seals were not sealing tight. They had degraded over the 30+ years the originals had been in the bike. New push-type seat from Georgefix cured the problem.

I had fuel come out the airbox a second time about 2 months ago. Had the petcocks turned offn (forgot to turn them ON), bike on the sidestand in the driveway, warming up to take a run to the store. I starved it out of fuel with the petcocks off, and when I turned them back on and re-fired the engine, fuel started dumping out the airbox. All I can think of is a needle or float stuck when it ran out of gas and on the sidestand, gave it an angle and fuel situation that is not conducive to good needle/float function.

Turned off the fuel and shut the bike down, tapped on the bowls, and it's been fine ever since.

[jetmechmarty]

Turned off the fuel and shut the bike down, tapped on the bowls, and it's been fine ever since.
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Howard

I've been going through that and it isn't fine any more. New needles and seats are at the house waiting for me.

[Bonz]

Yeah, good deal that you have new needles and seats. When I put my new seats in, I realized that the "easy finger/almost drop in seating" with the old ones was not the proper way they fit. I had to really work the new ones in with a little spit and such to help them slide. My first reaction was they were too tight, but nope, the new ones were just right.

[conquest87tsi]

Gas in Oil

So I am having this same issue.
I have a 1979 XS1100 Special with petcocks that are able to be shut off. I have been shutting off my petcocks everytime I park my bike and was still getting fuel in the oil.
So I cleaned the carbs, and the same thing, still getting fuel in the oil. So now I've just been shutting off the fuel and running the carbs dry. Kind off sucks when I'm running around town, have gotten pretty good at estimating how long it will last when I shut them off though.
I guess my question is:
Is there somewhere specific I should be cleaning in the carbs? If anyone has a picture is would help greatly.
Also, shouldn't the intake valves seal the intake from fuel entering the combustion chamber?

Please someone help, I'm tired of changing oil every couple weeks.

[bikerphil]

Time to clean/rebuild the petcocks for positive fuel shutoff. Also time to replace the worn needle/seats (float valves) in the carbs.

[conquest87tsi]

Fuel in Oil

Like I said, with the petcocks I have, I am able to shut the petcocks off. They do not leak, as I am able to run it dry and there is no fuel in the lines. As far as a carb rebuild, do most kits come with what I'm need?

[bikerphil]

Like I said, with the petcocks I have, I am able to shut the petcocks off. They do not leak, as I am able to run it dry and there is no fuel in the lines. As far as a carb rebuild, do most kits come with what I'm need?

With your early type carbs, you probably will need just the needle/seat and possibly float bowl gaskets.

[natemoen]

How do you know you are getting gas in the oil?

As to the valves sealing the gas out, there will always be at least 1 valves open.

[James England]

You should be able to have your gas tap in the on position and not get fuel overflowing from the carb bowl(s). The needle valves, lifted by the floats into the seats, should seal the fuel supply off. It's probably only one carb that's leaking ie the needle valve is not closing properly and therefore not stopping the fuel flow. The needle valve may have dirt/rust/whatever stuck in it. The float may be damaged, or leaking and not closing off the needle properly. However, the float needle/seat/float may be functioning properly and have nothing wrong with it...except that the float level is set too high. There's a metal tang on the float which pushes the needle.

1. Compare the floats and see if there is a tang noticeably different from the rest.

2. Check the floats for dings and leaks

3. Replace the float needles and seats, checking the small hemispherical filters above the seats whilst you're in there.