float level

[gs newbie]

what is the float level and what happens if it is too high/low?

[GRU]

nobody knows!!!!          hehe

i just know that it should be at the level with the gasket which seperates the float bowls with the carb....

basicly, if the float hight is high then that means that the gas inside the carb is higher then it should be and it will start leaking inside your engine or to the air filter

[Kerry]

Sorry for the   LONG   answer.  I chose to answer a few unasked questions while I was at it....

Let's take a detour and talk about the hardware in your toilet tank.  

No, I'm serious!  If you know how a toilet works, the floats in a carburetor will be a piece of cake to understand.

Let's say you just replaced your toilet tank (reinstalled your carburetors).  Before the toilet (carb) is ready for use you have to open the valve on the cold water supply line (turn the petcock to the PRI position) to fill the tank (float bowl).  The water (fuel) flows in and the level rises until the float is pushed up and closes the supply valve (float valve or needle valve).

With your toilet you can lift the lid on the tank and SEE where the water level (float level) is.  With carburetors the best way to determine the float level empirically is like this.

OK, enough about toilets.  The following 2 paragraphs are conjecture on my part, and I'm open to correction.  But, here goes....

If the float level in your carburetor is too low then the vacuum created in the upper half of the carb body won't be able to suck enough fuel up through the jets - to be mixed with air on its way to the cylinders.

If the float level is too high, then ... the carbs will flood too easily?

===================================

One thing I do know: as fuel is sucked out of the bowl and up through the jets, the fuel level (and therefore the float) drops and the float valve opens to allow more fuel in.

When the petcock is in the ON or RES position, fuel is "pumped" into the float bowl as long as the engine is running.  The "pump" is a flexible, vacuum-actuated diaphragm in the petcock.  (The vacuum is applied via a thin hose from the left carburetor.)  When the engine is turned off, no fuel will flow into the float bowl even if it were drained completely and the float went to its lowest possible position and the float valve were wide open............I think.

When the petcock is in the PRI position, the "pump" is bypassed and gravity pulls fuel all the way to the carbs.  Here we're back to the toilet analogy: If the float bowl is not yet "full" then the floats will be below the "float level" and the float valve will be open, and fuel will flow in until the floats rise far enough to close the valve.

Let's say the tip of the float valve is worn, or some grit prevents a tight seal with the float valve seat.  If the petcock is set to PRI, fuel will continue to flow (at a slower-than-usual rate because of the SMALL, not-supposed-to-be-there opening).  How long will the fuel flow?  Until it reaches the level of the fuel in the gas tank - that's how siphoning works, right?

The last time I checked, my carbs were entirely BELOW my fuel tank, so what's gonna happen?  The fuel level will rise up through the jets, into the top part of the carburetor, and out whichever "exit" is the lowest.  I'm not sure whether that would be the rubber boots that attach the carbs to the airbox, or the rubber boots that attach the carbs to the engine block.  Filling the airbox with fuel is not a good thing, but filling a cylinder is far worse because it can lead to "hydro lock" - where the starter tries to compress FUEL in the cylinder rather than AIR, and you bend a connecting rod ... or something like that.

EDIT: Changed link from sisna.com to bbburma.net.