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2022/04/23 15:12:00

elmo14

Gas in oil, Kawasaki FH500V

I had a strong gas smell from the oil when I change it. I read that the leading cause is leaving the fuel shutoff valve open in storage. So I changed the oil and made sure to always close the valve. After a few cuttings, I have a gas smell again in the oil which is translucent brown, not black. So I am wondering what the second leading cause of gas in oil? Here are my observations:

The engine has 1000 hrs on it
Two, maybe three years ago one of the pushrods bent like a hockey stick. Don't know what caused that, the valve moved freely and hasn't reoccured.
The compression is 100 psi in one cylinder and 90 psi in the other. The manual says 57psi and that higher readings could be from carbon buildup.
Under no load, the engine runs fine on the 100 psi cylinder only and runs poorly on the 90 psi cylinder only.
Sparkplugs from both cylinders look normal, dry with no oil or other deposits.

Any suggestions on what to look at would be great. I'll probably change the oil and adjust the valves in the meantime.

6 comments Leave a comment

Conrad Sigona

The typical problem is that the float valve in the carburetor fails to stop the flow of fuel. It could be that a little bit of crud is stuck in the valve, that the seat of the valve is uneven, or that the tip of the needle (often rubber tipped) is hardened and no longer sealing.

The fuel shutoff valve is just a circumvention, not a solution. It works in that the fuel in the tank, if the tank is higher than the carburetor, is drawn by gravity. If the float valve is not sealing, fuel will fill the carburetor bowl and overflow down the throat and into the cylinder, past the rings and into the crankcase. By shutting off the shutoff valve, you've stopped the flow, so the carburetor won't overflow while the engine is idle.

I suggest you drain the carburetor, remove it from the engine, open up the bowl and clean it out. Examine the float to see if it moves freely. Remove the float and examine the needle valve and seat. Clean as needed. When you're finished, or think you are, test the float valve with air. Just put the fuel inlet to your lips and blow slightly. When the carburetor is upright, air will go through, but when you invert it, the float valve should close and stop your air.

Note, however, that if the carburetor is overflowing like I suggested, the engine will run poorly at idle, since it's getting too much fuel and the fuel is not well regulated. If the float is indeed the problem, this is a quick and cheap fix.

2022/04/23 15:38:42

SRTsFZ6

Looking at your engine spec's, you have "pulse" fuel pump.

It uses the crankcase pulses to pump the fuel to the carb.
If it's leaking internally, it'll leak fuel into the crankcase..

That'd be my first bet...

.

2022/04/23 16:27:06

SRTsFZ6

I believe you have a pulse type fuel pump that uses crankcase pulses to push fuel to the carb.
If the internal diaphram is leaking, it'll go into the crankcase...

That'd be my first bet..

2022/04/23 16:29:02

Conrad Sigona

SRTsFZ6's analysis makes lots of sense. If the diaphragm is leaking, as he suggests, it would not affect the running of the engine, since the leaked fuel is not going into the carburetor or cylinder at all; it goes right into the crankcase. Follow his hunch before you follow mine.

2022/04/23 17:04:52

SRTsFZ6

Conrad, your first post doesn't show, "approval pending"....

2022/04/24 08:23:15

Conrad Sigona

Just as well. It's no good.

2022/04/24 08:48:46

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Gas in oil, Kawasaki FH500V

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