Can gas still get into oil if fuel supply is shut off?

[Courtney]

I'm just wondering if it's still possible for the fuel to get into the crankcase if I have a manual petcock that is working correctly and is shut off? Reason I ask is I detect the slightest smell of gas from my crankcase after a fresh oil change, and leaving the bike sitting for a week after running it. I turned the petcock off at the end of the run, but this morning detect a smell of fuel???

[IanDMacDonald]

Well, un-burned fuel from the petcocks , anything else could be fuel vapor or exhaust gases in the crank case?

[MPittma100]

Fuel in Oil

I'm just wondering if it's still possible for the fuel to get into the crankcase if I have a manual petcock that is working correctly and is shut off? Reason I ask is I detect the slightest smell of gas from my crankcase after a fresh oil change, and leaving the bike sitting for a week after running it. I turned the petcock off at the end of the run, but this morning detect a smell of fuel???

The answer is yes. Any one of the four carbs float valves could leak. Even though the petcock(s) is closed, there is still some residual fuel in the lines that would deplete if a float valve is not sealing.

Fuel that gets into the crankcase is fuel that has leaked into the carb holders. Then it goes into the cylinder and by the rings.

A good way to prevent this from happening is to either park the bike so that the rear is downhill on the center stand or, if level, put a 2X4 or equivalent under the front tire. The idea is to get the gas that does get into the holders to run the opposite way - into the air box. This is a good option for long term parking. Can also put a towel or other absorbent material underneath the air box to protect the engine finish.

Unfortunately, we cannot predict when any one of the carbs may start to leak.

Mike

[BA80]

Or fix the carbs............

[Courtney]

Or fix the carbs............

Yep, but time to investigate further first.

[motoman]

Yep, but time to investigate further first.

........which, as Greg stated, will lead you to 'fixing' the carbs. You got one or more float needles not seating.

[Courtney]

Yeah, that's the piss off, after redoing them properly, setting everything up perfectly there'll prob turn out to be some little piece of **** sitting on the edge of a seat. And that's with no less than 2 inline filters...... Man I'm tired of doing everything right to have it turn out wrong.

........which, as Greg stated, will lead you to 'fixing' the carbs. You got one or more float needles not seating.

[TopCatGr58]

Hey Courtney,

I can't remember the specs/stats for your bike, like how many miles the topend has seen....what your compression values are/were??

Like others have said, could be leaking float valves, could also be worn rings allowing vapors left over in the crankcase??

Hope you find it to be something easy/simple.

T.C.

[MPittma100]

Fuel in Oil?

Yeah, that's the piss off, after redoing them properly, setting everything up perfectly there'll prob turn out to be some little piece of **** sitting on the edge of a seat. And that's with no less than 2 inline filters...... Man I'm tired of doing everything right to have it turn out wrong.

Getting all four carburetors set exactly right commonly takes more than one attempt. Pulling them apart a second or third time has happened to everyone who has been brave enough to try it.

A good idea for the least amount of frustration is to fill the carbs with gas OFF of the bike first. You should even tilt them to the left side to simulate the bike being on the kick stand. Let them stay there long enough to insure there are no leaks. You will be much happier doing this than finding out you have a leak once they are installed. A leak repair after rebuild is often as simple as tapping the bowl.

The probability that trash is created in the fuel system when you R & R the carbs is high. Foreign objects can come from inside of fuel lines, from the tank, petcocks, etc. After installing filters, replacing fuel lines, or just having some of the lines/fittings apart, it is a good idea to let some fuel run out of the lines prior to hooking them back up to the carbs. This will allow any trash to get out and not go to the float valves.

If you do get the carburetors right the first time, you need to kiss your rabbit foot because you just got lucky.

Mike