Float Height - Carb Drip II

Tue Nov 19, 2013 4:33 pm

My float is apparently allowing the fuel level in the float bowl to be too high, so that fuel finds its way (via the semi-circular channel around the venturi area) to the hole over the choke and down to the drip hole. I think I need to lower the float so that it closes the needle valve sooner, but that doesn't jibe with diagram in the service manual (forwarded by Don McCombs) or the diagram that came with the carb rebuilding kit. (The new needle valve seems to have the same dimensions as the old one, and it seems to seal properly when closed.)

At its maximum height (closing the needle valve), the bottom of the float is now about 1 1/2 " (maybe 1 15/32 " ) below the gasket surface of the throttle body. The diagram in the service manual calls for that dimension to be 1 13/32 ". If I raise the float to that height, it seems I will guarantee that the float bowl will overflow.

The diagrams appear to show the top of the float even with the joint between the 2 halves of the carb, specifically even with the top surface of the gasket. The top of my float is now about 5/32 " below that surface.

It seems logical to me that I have to lower the float (to close the needle valve sooner), not raise it as called for by the manual. What am I missing?!!

Re: Float Height - Carb Drip II

Tue Nov 19, 2013 5:09 pm

Brian, Let me try and explain this in a different way which hopefully will be easier to visualize. Hold the top upside down so the manifold flange is facing up. With the body gasket in place, measure from the top of the cork gasket to the top of the float (as it now sits). That measurement should be 1.4" (1 13/32"). Adjust ment is made by carefully bending the brass hinge next to the float with some needle nose or other small pliers. Now turn the top right side up. The float will drop, opening the needle valve. The distance from the bottom of the gasket to the bottom of the float should be 1.6" (1 19/32"). Adjustment is made by carefully bending the little vertical brass tab that hits the needle valve seat. Make sure the float is centered in the depression of the top and not twisted which could allow it to hit the side and bind. Give that a try and post back if that still doesn't seem right on your carb.

Bob

Re: Float Height - Carb Drip II

Tue Nov 19, 2013 5:12 pm

Brian50 wrote:My float is apparently allowing the fuel level in the float bowl to be too high...

Maybe. Maybe not. Use the technique described on Pages 2-5 and 2-6 of the Cub Service Manual GSS-1411 as shown below. That will determine the actual condition inside the carburetor. Report back with your results.

http://www.cleancomputes.com/Cub/Blue%2 ... -02-05.jpg

Re: Float Height - Carb Drip II

Tue Nov 19, 2013 9:10 pm

Hm, looks like I need to create a tool FES 36-3. Seems like a spare drain plug needs to have a hole drilled up the center and be filed round to fit some clear tubing. Nice way to confirm the level in the float chamber. I assume the "specified fuel level" is the 9/16" to 5/8" shown on page 2-2 and on the drawing on page 2-9? There must be something radically wrong in my float chamber - I'll see what I can find. You guys are good. Thanks

Re: Float Height - Carb Drip II

Tue Nov 19, 2013 9:18 pm

Brian50 wrote:Hm, looks like I need to create a tool FES 36-3. Seems like a spare drain plug needs to have a hole drilled up the center and be filed round to fit some clear tubing. There must be something radically wrong in my float chamber - I'll see what I can find.
Well stocked hardware store, plumbing section, plastic hose barbs and tubing. Inexpensive.

You mentioned a new kit for the carburetor. Some parts in off brand kits do not fit well.

Following is some of my earlier posts on bench testing carburetors. I use the plastic hose barbs and plastic tubing from the hardware store.

Eugene wrote:Check for a fault in the needle valve and seat area.

Bench test for fault. Carburetor top upside down on bench. Plastic hose connected to carb inlet. Elevate plastic hose and fill with rubbing alcohol.


Eugene wrote:Use the Service Manual, fuel system section. Following is how I bench test my Cub carburetors for fuel level in the bowl. Leaks will also show up during the bench tests. I use a plastic hose on the carburetor inlet, use rubbing alcohol, pour alcohol in the inlet hose and check fluid level in carburetor bowl.

Below is with the carburetor installed on the tractor.
Get a hose barb to fit the carburetor bowl drain hole and about 3 feet of clear plastic tubing to fit the barb. Install the barb and plastic hose. Hold the open end of the hose close to and above the carburetor. Turn on the fuel at the gas tank. Measure from the top of the fuel in the hose to the top of the bowl. Fuel level should be 9/16 to 5/8" below the two carburetor halves.

Re: Float Height - Carb Drip II

Wed Nov 20, 2013 1:29 pm

If you can't find a hose barb with the right threads, check the zerk selection. that's what I did - then drilled out the spring and ball. Tubing slips over the nipple on the zerk.

Re: Float Height - Carb Drip II

Thu Nov 21, 2013 4:32 pm

After buying a brass plug and drilling through it, I went to my local hardware to get some plastic tubing and discovered threaded barbs (I hadn't known about them). Checked the fuel level in the float bowl using the barb/tubing system - level is about 1/4" too high. Will adjust float and re-check. No leaks apparent although somehow I managed to cross-thread the iron drain plug. Jeez. I will double check with alcohol.

Will Teflon tape on the drain plug stand up to gasoline?

Re-checked that valves are not stuck - visual through spark plug hole with wife cranking. Operating the crank, that is, she's not cranky. Good cook too.

Figured I'd do a compression check as suggested while I have the tank off again, but my childhood comp. gauge doesn't have a 7/8" adapter. Wonder where I might find one.

Will report back further.

Re: Float Height - Carb Drip II

Thu Nov 21, 2013 4:36 pm

Teflon is gasoline resistant. You might see if one of the local auto parts stores will lend/rent you a compression tester.

Bob