Gas coming out of the exhaust on start up

[don white]

I just went through the same thing with an 18 Kohler engine. Smell the oil I bet it smells like gas and I bet the oil level is high. The float needle valve has a rubber tip and it does not like ethanol. I am told this is a very common problem. You can just put a shutoff valve on the fuel line but that won't solve the problem. Everytime you shut down the engine some fuel will run into the cylinders. You need a carb rebuild kit.

 

[David_Kb7uns]

Had a 1999 Murray with a 19.5HP Briggs twin that you had to run partial choke on because the low speed jet was plugged. Ran a half bottle of Berryman b12 chemtooln through the carb and after cleaning the jet out twice more the inside of the carb now is just about as clean as new. Had a push type line more that had not been run in over a year and ran rough on start up and poured Seafoam in the tank and ran for another 15 minutes or so and you could hear it clear up and run smooth. So I am now becoming a believer of some of these fuel additives and try them before a carb disassembly.

David Kb7uns

 

[yelbike]

Well tonight i finally had time to pull the carb out and apart. I cleaned it good, there wasn't much of anything inside as for gunk or sediments. So i still quite stumped as to why it sprays gas out the exhaust on cold start up. What else could it be?

 

[yelbike]

I agree with the fuel shut-off but just wondering if you checked the oil to see if gas has gotten into it?

No gas in the oil.

 

[George the Beagle]

I agree with Don White. This is a very common problem.

 

[JOHNINMA]

Is it possible the air filter is dirty enough to be acting like a choke and causing it to pull excessive fuel from the carb.???

 

[yelbike]

Is it possible the air filter is dirty enough to be acting like a choke and causing it to pull excessive fuel from the carb.???

Thanks, but nope. I changed both filters in the spring and i blow it clean every few hours with compressed air just like they say not to do.

 

[crazyal]

Did you try shutting off the fuel to see if it stops the problem? If it does then I would say either the float valve is leaking or the carb has a defect where a tiny bit of gas is getting around the float valve. Not enough to cause you issues while the engine is running but after a week of sitting enough leaks by to cause you starting problems. One test I like to do when I have the carb off is to blow air (by mouth on a clean hose) where the gas goes into the carb. With it upright air should go in freely but upside down the needle valve will not allow it to enter. Riding mowers have an electronic shut off valve that may prevent the test from working unless you energize it.

 

[BeezFun]

Install a spark plug in the exhaust, you'll have an afterburner.
I have a 25 hp kaw in my Toro ZTR, it has a fuel pump. If yours has a fuel pump it can't be leaking fuel by gravity into the carb or cylinders. One test you could do is remove a spark plug before you try a cold start and see if there's really fuel in the cylinder, either by the sniff test or poking end of rag in there to see if it gets any fuel on it. If no fuel, the problem is narrowed down to something during the cold start, which points to the choke and running way too rich on startup.