The float circuit controls the amount of gas in the fuel bowl throughout the operating range of the engine. As the gas lowers in the bowl, the float drops and allows the needle to pull out of the seat allowing fuel to flow into the bowl. Some Marvel Scheblers use a fuel pump to push gas to the carburetor and some use a gravity feed from the gas tank.
The Marvel Schebler float is a two pontoon type which wraps around the nozzle. This is designed so that the engine can operate at angles up to 45 degrees.
Most fuel flooding problems are caused by dirt getting into the needle & seat. A dirty gas tank can send up particles after a carburetor cleaning and lodge in the needle. Never put pressure on the needle when adjusting the float. Replace the needle & seat anytime you rebuild the carburetor. New needles have a viton tip and wiping off the tip with mineral spirits before installing will help the initial seal, otherwise it may take 10 starts to get the residue off.
Test your float for leaks. Heat up a pan of water and just prior to boiling immerse the brass float. Any leak will show up with bubbles in the water.
Set the float level as per specifications. The level is not the same for all MS carburetors. Don’t fudge the level. Doing so will cause other running problems.
Gas tank should be clean, filters changed. If the screen is missing from the fuel inlet then attach an in-line filter between the fuel pump and the carburetor. This will keep most of the junk out of the carburetor.
We have two different floats for the MS carburetor. One is for the 4″ bowl length and the other is for the bigger 5″ bowl length. Click on the floats to see the product page.
The economizer jet is not used in all TSX Marvel Scheblers. Some installations require a leaner condition so the economizer jet is added. You can spot the 2 jets by taking the top and float bowl apart. On the top of the float bowl there will be 1 jet, which is the idle jet, or 2 jets, the 2nd jet being the economizer.
The main jet is at the bottom of the fuel bowl. In the illustration there is an adjusting needle which not all Marvel Scheblers have. This adjustment allows you to adjust to different applications.
Look for 2 holes at the bottom of the float bowl. Be sure these are clear. You can blow air through the holes to check. They may be covered with so much gunk that you can’t see the holes.
