Fuel in crankcase – how much is too much?

[Andrew Vanis]

Fuel in crankcase – how much is too much?

As I’ve been rebuilding my carburetor and reading all the posts, made me wonder….how much is too much?

I get that if both the carb fuel valve and the gas tank fuel valve fail and and 4 gallons go in it’s an issue.

However if the tank valve works and the carb valve fails (even on one carb), the contents of the fuel hose can drain past the carb. Maybe that happens infrequently, many it happens after each ride.

Thoughts?

[tom203]

Get a new petcock to eliminate it as a problem- then you have to contend with leaky needle seats. But these might not leak enough to be a problem as bike will be running and consuming fuel. You don't want fuel in your crankcase.

[Agemax]

a small amount like the contents of the fuel line will not hurt at all. it will soon evaporate and will not be harmful to the engine or the oil

[Crage]

It's an issue when you can tell that your oil level is rising in the sight glass.

[chuck hahn]

Here is my personal standard. If I forget the petcock on PRI... or anything else that even BRINGS THE QUESTION TO MIND.. the engine doesn't get started and the oil is drained and new put in. 15 bucks of oil is cheaper than any second guessing.

[tkent02]

Meh, a little gasoline doesn't hurt anything. They put it in airplane engines on purpose to thin the oil out for cold weather, those engines are expensive. Once the engine is hot it just evaporates away.

Too much is not good as it lowers the viscosity of the oil to the point the engine isn't being lubricated properly. Probably what Crage said is a good guideline to be on the safe side. If it didn't come up noticeably in the window I woudn't even worry about it.

[Brendan W]

The short answer is the F mark on the case.
I reckon sumps are designed for a certain amount of fuel finding it's way down and at the time the GS was designed evaporation and oil changes probably took care of it. By certain amount I mean imperceptible in the course of normal operation.
Gasoline has lots of different things in it. These have boiling points ranging from 100 to 400F and more, so it may be some rethink on the evaporation theory is needed if you loose a lot to the sump. We have a crazy situation in Europe where main dealers are filling auto sumps to the min at service time to compensate for fuel wash induced rising oil levels ( diesel engined cars mainly)
Increasingly gasoline is doped with Ethanol which has the 'benefit' of absorbing water and separating out from the gas as aqueous ethanol. I'm no chemist but I don't like the sound of that laying around the oil pan.

On balance I would lean towards Chuck's approach - if I am noticing fuel getting in there I need to do something about it.

[Andrew Vanis]

The short answer is the F mark on the case.

This sounds reasonable

Get a new petcock to eliminate it as a problem- then you have to contend with leaky needle seats. But these might not leak enough to be a problem as bike will be running and consuming fuel. You don't want fuel in your crankcase.

Already did. (This was not a "Help me, my petcock is leaking" post.) Adding the manual shut-off is for the inevitable failing OEM automatic fuel stop tech. Extra insurance you can say.

Here is my personal standard. If I forget the petcock on PRI... or anything else that even BRINGS THE QUESTION TO MIND.. the engine doesn't get started and the oil is drained and new put in. 15 bucks of oil is cheaper than any second guessing.

With that standard, you’d be changing every ride since it is POSSIBLE that some fuel got in.

a small amount like the contents of the fuel line will not hurt at all. it will soon evaporate and will not be harmful to the engine or the oil

Meh, a little gasoline doesn't hurt anything. They put it in airplane engines on purpose to thin the oil out for cold weather, those engines are expensive. Once the engine is hot it just evaporates away.

These also sounds reasonable.

[chuck hahn]

Use some common sense here Andrew...No I don't change it before every ride, but I do look at the levels before very ride. If its risen from where it should be OR like I said that I discover I had forgotten to take the petcock off PRI, I smell the oil and if I even have a suspicion..then yes I change it erring to the side of better safe than sorry.

Once you've had a GS for awhile and are particularly familiar with it..youll develope a sense of whats what and calm down. And I also am 100% positive3 of my petcocks also..they dont leak. Someone mentioned blow by gasses too..which ( if the airbox is on ) get sucked back thru the crabs and reburned..so that's not a real concern either.

[tom203]

I check my petcock for correct operation when I reinstall the tank in spring. I look at oil level almost before every ride- any weirdness would make me curious as to why.

[Andrew Vanis]

I check my petcock for correct operation when I reinstall the tank in spring. I look at oil level almost before every ride- any weirdness would make me curious as to why.

a good time to check but why re install tank? drain and store? (or is this another BassCliff article I haven't discovered yet?)

I think the owners manual says to top it off.

[chuck hahn]

Most folks usually do things like carb cleaning, valve adjustments, clean wiring harness connections etc etc during the off season and remove the tanks.

[Octain]

I agree with the "F" mark opinion. Obviously, you don't want your oil level above the "F" mark. (or below the "F" mark for that matter)

[tkent02]

Most folks usually do things like carb cleaning, valve adjustments, clean wiring harness connections etc etc during the off season and remove the tanks.

I'd rather ride all winter.

[JEEPRUSTY]

One day all shall be revealed.

I think if oil smells of gas it should be changed as you are changing the oils viscosity and I have no way of knowing if the gasoline will not alter the oil's chemistry.

I do not think its just a simple thing like a petroleum distillation.