This could mean gas is flowing over the top, out the vent, or even out of the throttle shaft.
Here are some possible reasons:
- Needle & seat leaking.
- Float leaking and filling with gas.
- Fuel pump putting out too much pressure. Should be under 4 lbs.
- Float rubbing, or catching because of worn float shaft.
Doesn’t Run Unless Choke is Closed
There is too much air, or not enough gas.
- Check for leaks around the throttle shaft (where the shaft comes out of the throttle body). This is caused by worn shaft. Re-bush.
- Mounting gasket is leaking.
- Not enough fuel.
- Weak fuel pump.
- kinked fuel line.
- Non ethanol resistant rubber fuel hose. These can collapse inside.
- Old gas has turned and coated the inside of the carburetor with varnish.
- Plugged, or dirty passages.
- Check the idle pickup tube. They are often plugged. Cleaners will not get them unplugged.
Some engines like Kaiser Willys does not need the vacuum advance in the YF carburetor. Plug with 1/8 pipe.