marvel schebler carb

1. Inline filter: Gotta flow a steady stream of gas-not a dribble. Lots of the new in-line filters are for cars with pump in tank, so it goes through the filter under pressure and they don't gravity flow too well.

2. Had a small engine carb give me fits 2 weeks ago, the elbow going into the carb was choked.

3. Float level on about all the M/S TSX series is 1/4" with gasket, 5/16" without. 3/16" is gonna be too rich.

4. Does the float move freely in the bowl?

5. If your carb has a tiny jet in the bowl feeding the main nozzle and no main fuel adjustment the problem is probably in the passage below that jet.

Wow. Too much info! After my 2 cents worth is a description of the idle & starting circuit functions. See if you can figure out the problem.

This appears to be a throttle valve and/or idle mixture problem.

Float adjustment isn't an issue in starting if fuel bowl has gas in it. If the bowl has gas and the engine vacuum is ok, some things to check:

1. The throttle plate must be installed with the angle identification mark facing up.

2. The idle jet must be fully seated and w/o any tool marks in the slot that can distort the orifice.

For starting and idling the throttle valve should be set slightly open with the edge between the primary and the secondary idle orifices.

With the valve in this position, the air pressure (manifold vacuum) at the primary is lower than the air press in the fuel bowl and fuel is force from the bowl up the idle fuel passage passing through the idle jet.

Air for atomizing enters at the idle adjusting needle seat mixing with the gas. The atomizing process is repeated at the fixed secondary idle orifice.

The rich mixture of gas & air emerges from the primary idle orifice and is reduced to correct proportions by the air that passes around the slightly open throttle valve.

The idle mixture screw can either control the air (air adjusting) or the fuel (fuel adjusting) to provide the correct mixture for starting and idling. Most MS are air adjusting as in the pix, turn cw to richen, ccw for leaner. Fuel adjusting is the opposite.

Joe

The only thing that is germane to starting and idling is shown in that picture plus the pressure differential provided by the cranking engine.

The main function of the venturi is to atomize the fuel. When the throttle valve is closed that function is assumed by the bevel on the throttle plate. That is why it is important to have the correct plate and that it is not installed upside down.

For starting and idling, as long as the bowl has fuel and atmospheric pressure, it doesn’t matter if the float level was set at 1/8” or 1/2”, It doesn’t matter if the fuel line is connected to the carb, it doesn’t matter if the power mixture valve is shut disabling the entire power fuel circuit. So why address everything from the gas tank vented cap to the main jet? It’s irrelevant to this post.

Perhaps I am misreading the question in the initial post. If so I apologize in advance and will slink away. In fact the sun is shining here finally after a week of daily rain. I am going out and play with my tractors. Joe

I soak the whole thing in B12 Chemtool overnight, rebuild it in the morning, get the float level right, back out the screws per the instructions, and it will run for you.

--->Paul

What is the history of the problem... was it working, and you did a tuneup, or did it sit for years without being run and you are trying to get it going?

What style is the carb, updraft or downdraft, and what is the tag number?

Check for an air leak that may be contributing. Put you hand over the carb throat and crank the engine with the choke open. Do you have a good vacuum? Is the intake manifold tight, no visible gaps in the gasket?

Joe