Fuel in Oil

[rancher_mac]

It appears I’m getting fuel in my oil. I thought maybe it was a carb so I replaced and I still have the oil level increasing after a mow. I just checked compression and one cylinder is 95psi and the other is 100psi. Any thoughts as to what the cause might be? it is a twin opposed Briggs 42a707-2238-e1.
I should add that both cylinders are running. New spark plugs this season and the both look great when removed.

I also checked my Tecumseh 195ea and it had 90psi. Is that low enough to work on the valves?

 

[bertsmobile1]

Loosen the carb mountings and slide it 1/4" or there abouts off the engine
Leave everything connected
If the carb is failing then that will stop fuel entering the cylinder and you will see fuel dripping from the engine side of the carb
In very rare cases a ruptured diaphragm on an impulse pump can cause fuel to leak back down the impulse line

 

[tkos115]

I second checking the carb by sliding it back away from the engine. As mentioned, it's possable that the fuel pump diagram is bad internally. That would cause fuel to get into the oil, but not really cause a running/rich issue. I had this happen on a twin briggs a few years ago. Do you notice the oil level going up if it sits between uses or only after running it? Basically fuel can only get into the oil from a bad carb, or fuel pump. So check both of those areas out. If this model doesn't use a fuel pump then that just leaves the carburetor. Being that your only noticing the oil level going up after use, I'd suspect a bad fuel pump diaphragm since generally if it's leaking through the carb when it's running it will usually cause a rich condition.

 

[slomo]

Flip the carb over. Pressure test the needle and seat at 7psi for an hour. WET the needle while testing with some spray oil.

Carb float level should be parallel to the carb body, bowl mounting surface.

Flush the fuel system. Might have trash getting into the carb causing this.

Once the carb is not throwing up, dump the oil several times.

 

[rancher_mac]

Flip the carb over. Pressure test the needle and seat at 7psi for an hour. WET the needle while testing with some spray oil.

Carb float level should be parallel to the carb body, bowl mounting surface.

Flush the fuel system. Might have trash getting into the carb causing this.

Once the carb is not throwing up, dump the oil several times.

Sounds great. I almost have all the supplies to work through some of this again. Just waiting on USPS. Would you suggest unassigned oil, running a bit, then repeating the process a few times? Maybe using an engine flush or something like sea foam?

 

[hlw49]

Guys in his original post he said it is an opposed twin not a V Twin and the fuel pump is an intergerated part of the carb. So what you are saying about sliding the carb back to stop it from leaking fuel into the engine will not work. 42a707-2238-e1 is an opposed twin and does not have a bowl type carb. The bottom half of the carb housing holds the fuel. These carbs are very easy to clean just take the top off and clean the orficeses and blow out with compressed air. But be careful with the low speed welch plug you can blow it out and won't be able to find it.

 

[slomo]

Guys in his original post he said it is an opposed twin not a V Twin and the fuel pump is an intergerated part of the carb. So what you are saying about sliding the carb back to stop it from leaking fuel into the engine will not work. 42a707-2238-e1 is an opposed twin and does not have a bowl type carb. The bottom half of the carb housing holds the fuel. These carbs are very easy to clean just take the top off and clean the orficeses and blow out with compressed air. But be careful with the low speed welch plug you can blow it out and won't be able to find it.

Good to know. All in effort to get a good running carb.

 

[slomo]

Sounds great. I almost have all the supplies to work through some of this again. Just waiting on USPS. Would you suggest unassigned oil, running a bit, then repeating the process a few times? Maybe using an engine flush or something like sea foam?

SAE 30w is all you need.

Adding solvents like nofoam or marvel wonder oil is a waste of money and not the prescribed oil weight/grade. Mainly solvents degrade the main oil down off it's viscosity value. These hot running air cooled engines don't need any help to thin their oil down.

 

[Forest#2]

Your compression is ok.
Since that is the old opposed twin it very rare for fuel to get into the oil with the pump on the front of the carb type and you say you replaced the carb.

You say it APPEARS that fuel is getting in the oil.
Describe APPEARS?

 

[rancher_mac]

Your compression is ok.
Since that is the old opposed twin it very rare for fuel to get into the oil with the pump on the front of the carb type and you say you replaced the carb.

You say it APPEARS that fuel is getting in the oil.
Describe APPEARS?

good question, I say appear because the the oil is about 1/8” up the dipstick when I check it about an hour after use. It’s not a lot and it’s hard to smell gas, but I don’t know any other reason why it would be increasing. I’m thinking this would be more from a leak down rom the carb after sitting. I didn’t want to try running it more to test this as I’m going to do some work on it. Right now I have some OEM gaskets on the way sometime today and then I’ll work on it when I can…not a lot of spare time on my hands lately so it may take a bit. While I have things apart I’ll probably check valves and clean carbon from the heads too. I’ll for sure keep you all updated though with what happens next.