What is Carb Spitback exactly?

Hi all, I'm looking through the fuel system troubleshooting section of my OMC service manual for my L115GLEDC, 1996 V4, 115hp looper as I am trying to hunt down a fuel leak up by the carbs.

I know I have a fuel leak when I squeeze the primer so I suspect gaskets or needle, etc.

What got my attention though is that although my motor runs really well, every time I remove the air silencer I see that with the motor off there is a small pool of fuel in the bottom of the black plastic throat opening to each carb, i.e. all 4 of them! My little 25hp Johnson, single carb, is same story. Is this normal? Or is this fuel spitback?

I figured it's normal, but manual says if you have fuel spitback to tear into the "leaf plates" on the intake manifold....which looks involved.

I'm hoping the wetness up there is typical, and that focusing on my leak from the supply line side of things is my only problem here.....

Re: What is Carb Spitback exactly?

If you have a faulty reed valve ("leaf" on the "leaf plate") it will cause the carb to spit fuel OUT of the carb throat. This will make the motor idle and run horribly---not your problem. A little fuel in the carb throat is normal. It shouldn't be dripping out all over the place, though. It's running well, and at worst a little rich. If it's not dirtying up your cowl pan, I wouldn't worry about it at all.

Re: What is Carb Spitback exactly?

You have to realize that the air flow going through there is in pulses, not a steady smooth breeze. Also, there is a lot of activity in there and what I'll take the liberty of calling an extremely stormy day, as such. At any rate hang around and you are going to get wet. A defective reed, on the other hand allows the air to actually blow backwards through the carburetor with every piston stroke.

Re: What is Carb Spitback exactly?

I always thought the pooling fuel was from a little leaking out of the carbs when i tilted up the motor.

Re: What is Carb Spitback exactly?

Spit back is normal on a 2 stroke. That's why you have an air box on it with a hose going to the intake manifold.

Re: What is Carb Spitback exactly?

larky said:

I always thought the pooling fuel was from a little leaking out of the carbs when i tilted up the motor.

Click to expand...

That too. Especially on older motors