Ferret Carb

[Malcolm Towrie]

Originally Posted by Jon Bradshaw

I have one on my trailer now that seems to idle fine with just the fuel in the carb, but will flood if I add a fuel line. It won't rev up and seems to need some tinkering. Is there a manual that shows step by step what needs to be done to adjust the carb to "factory" or end user settings? I am thinking if there was something that said- set screw #1 back off 1 and a half turns, set screw #2 back off 2 turns..... etc. Robin you may have some thoughts? Lots of experience tuning these....

I have linked to the manual above which shows the basic settings.

I found there are a few things that make these carbs run rich or flood.
The fuel needle valve that is closed by the float to maintain a constant level in the carb could be stuck partly open, so when you connect it to a pressurized supply, it passes too much fuel. This can also be because the floats are sticking on the pivot pin. Sometimes tapping the carb gently will free things up.

Someone has adjusted the float level too high. I have found the 3/4" level specified in the manual is a bit too high and the floats can hit the cover gasket before they close the needle valve fully.

If you are using an electric fuel pump in place of the stock mechanical pump, they often supply fuel at far too high a pressure, which overwhelms the needle valve and floods the carb.

Every one of the four or five carbs I have rebuilt has had the accelerator pump diaphragms leaking. I suspect this is an ethanol problem. The leak is directly into the intake manifold and makes the engine run really rich. It also allows the float chamber to drain down overnight. So a good check for this is, after the engine has been shut down for a few hours, look down through the carb with the throttle plates open for a large puddle of fuel sitting below the carb in the manifold.

Malcolm