Outdoor Power Equipment and Small Engines - Gas in Crankcase Kohler 18HP

Lawn Tractor:
Simplicity Regent model #1694749 purchased Oct. 2004

Engine: Kohler 18 HP Hydro model #CV492S
Carb: Kohlerengines part #12 853 117-S

Symptoms: exhaust smoke, hard starting, laboring, overfull "oil" level on dipstick.

Diagnosis: When checking the oil at drain valve, I discovered gas mixed with the oil. Thought of the fuel pump and possible leak past the seal there. Noticed excess gas at and around carb. Gas was getting into the crankcase.

Question 1: Is it possible gas is getting into the crankcase from the carburetor when idle?

Question 2: Would it be possible for the seat of the carburetor (needle and seat) to wear in such a way to have gas leak past and into the crankcase? Or could it be the rubber of the needle getting bad causing the leakage?

Question 3: Should the carburetor be replaced or can this be solved with a carb rebuild kit?

Have had problems with this engine in the past. This is not my mower. Taking care of my father-in-laws property. Had a renter last summer who was not very handy. I do know from past experience with the mower that it didn't run well at high or low throttle. It liked a middle position. What could have caused a problem like this?

Duplicate Question Posted

i would say you piston rings are worn or you have a bad cycl.

http://photo-shack.com/img/c86a7ee3d8ef0b551ed58e354a836f2b.gif

That was my first thought but how could that much gas be leaking into the crankcase. This was a new one on me. It has to get in there first before it could leak past the rings. No?

if gas is getting into the oil your carb is flooding. this is caused by the needle not seating so its not cutting off the gas. either rebuild the carb or replace it.

could be a stuck float in the carb, allowing gas to keep flowing from the tank, and into the crank case

if gas is getting into the oil your carb is flooding. this is caused by the needle not seating so its not cutting off the gas. either rebuild the carb or replace it.

Yes, that's what I thought the problem was. The question was if the seat of the carb could be worn to cause the gas to leak by.

Question 1: Yes, if your carburetor is flooding fuel through it, fuel can make it's way into the crankcase and dilute the engine oil.

Question 2: Yes and Yes, on both situations you described. The needle and seat is usually the culprit in this type of problem, but the seat can also have wear or another problem that will prevent a good needle from seating. The float in the carburetor can also be to blame if sticking, or leaking.

Question 3: Unless there is alot of corrosion in the carburetor or excess wear, a good cleaning and a rebuild kit will take care of the problems, in some instances a new carburetor maybe required.

kjcalig, I merged your 2 threads into 1 to avoid confusion and multiple answers to your question.

Thanks for the help. Wish I would have found this site sooner. I will definetly use it in the future. Keep up the great work!

Ok, I have to ask this question. I understand the gas leaking past the seat and sticky float. What are the chances that the carburator has to be replaced? I know that some newer carbs now have seats that are not replaceable and so a new carb would be needed. Is this the case with this carb? Do you know if there are carb rebuild kits for this particular carb? One more. How can you determine if the seat of the carb is the problem?

Rarely does the seat cause problems on your type carb. Clean it well with a q-tip soaked with carb cleaner, and twist it against the seat to get it clean. Install a new needle, and the problem will probably be solved.

What is the cylindrical shaped switch screwed in below the bowl ow the carb and what does it do?

Thats an after fire solenoid valve. It helps prevent fuel from entering the engine and igniting in the exhaust system of the engine, when it's shut down after running.

You can probably tell that I am trying to avoid buying a new carburator here. Could the selenoid valve have caused the problem of gas getting into the crankcase by holding the float up? Or from the description, does this prevent backfiring after turning the machine off?

No, the after fire solenoid blocks fuel from entering the main jet when the key is turned off. It will not cause, nor prevent a carburetor from flooding.