McCormick Carb Issues

[DanB53]

I got the W4 going by spraying gas in the throat of the carb. It will not run by itself. The carb has plenty of gas. When the fuel is turned on, fuel drips out of the air horn of the carb. But the engine doesn't get the fuel it needs to run. All the top end gaskets are brand new. The carb has been rebuilt. The valves were just ground and are seating. The manifold has no holes that I can detect. I hear a whistling from somewhere around the carb when it runs. Any suggestions?

[MIKE R]

Is the gasket between the carb and the manifold on and tightened down. A whistling comes from a large volume of air being forced through a small space. It the throttle shaft loose. If so air could be getting sucked in through there.

[DanB53]

They're all tight.

[MIKE R]

Maybe you need the air cleaner installed to give it the suction needed to lift the fuel.

[DanB53]

That's an idea. I didn't think of that. I'm not sure if that'll help anything but it's worth a shot.

[Jerry/MT]

I got the W4 going by spraying gas in the throat of the carb. It will not run by itself. The carb has plenty of gas. When the fuel is turned on, fuel drips out of the air horn of the carb. But the engine doesn't get the fuel it needs to run. All the top end gaskets are brand new. The carb has been rebuilt. The valves were just ground and are seating. The manifold has no holes that I can detect. I hear a whistling from somewhere around the carb when it runs. Any suggestions?

Fuel dripping out of the airhorn is an indication of improper float setting or a hung float. You have to pull the carb to check the float setting.
Before you do that, rap the side of the carb with a block of wood and see if the dripping stops. If the float pin and/or the pin fitting is worn or the float assembly is bent, it can rub on the wall of the fuel bowl and hang up allowing the fuel to over fill the bowl, and create an overly rich mixture that won't fire off.

To check for air leaks, CAREFULLY spray starting fluid around the throttle shaft, the carb to manifold gasket area and the cylinder head to manifold areas and with the engine running. When the engine speeds up, you've found you air leak. Look for cracks or rust holes in the intake manifold as these can also be a source of air leaks.

Rebuilding a carb is all about getting all the passages squeaky clean, not just replacing gaskets and needles. It usually means soaking it in carb cleaner for at least 24 hrs and then blowing out the passages and checking to make sure they are totally clear. You then set the float lever per spec and reassemble and then put the needles in.

[DanB53]

When I rebuilt the carb, it soaked for over a day. I replaced everything but the float. The float was adjusted to within a 32nd of an inch. I read somewhere that the gaskets in the new kits are sometimes too wide and the float rubs on them. Maybe that's it? And I checked for holes in the manifold when I painted it. All the gaskets are new.

[MIKE R]

It must be the gasket. I had the same issue on the cement mixer when I was fixing it. Put the old gasket back in and zoom it went.

[Jerry/MT]

When I rebuilt the carb, it soaked for over a day. I replaced everything but the float. The float was adjusted to within a 32nd of an inch. I read somewhere that the gaskets in the new kits are sometimes too wide and the float rubs on them. Maybe that's it? And I checked for holes in the manifold when I painted it. All the gaskets are new.

The point is that you need to do more than soak the carb, you have to blow out the passages with compressed air and then run small wires in them to make sure all the crap and corruption are out of them.

Did you check that the float was square with the world and not bent and the hinge wasn't worn or distorted? Were the floats leak free?( Put them in hot water and look for bubbles from a leaky float). Rebuilding a carb isn't had but it needs to be really, really cleaned well. What about the throttle shaft? Is it badly worn . Did you put in new shaft seals?? Putting new manifold gaskets on doesn't ensure good sealing. Check with starting fluid to make sure.

[DJ54]

There is also a small gasket sealing the metering nozzle, that comes up into the venturi/air horn, that could be leaking. Wondering if you took that out, and cleaned the very small cross drilled holes in that tube.