Carb question

Next time you shut it down turn off the gas. Next time after that turn on the gas and try to start it. If it starts easier then I think you have a float valve in the carb that is not fully shutting off the fuel flow and it's flooding the carb when it sits. Clean or replace the float valve but also be aware that some hollow floats can develope a pin hole in them and sink causing the fuel to never shut off. This is just my swag.

Edited by Stan IL&TN - 24 Dec 2016 at 7:21pm

Definitely check the float and the float needle valve. You need to replace seat and needle they do wear from vibration. A bent float can drag on the float bowl walls and keep it from closing the needle. A leaky float wont float. I like to check the carburetor off the engine with lung pressure. Float down and float bowl empty it should be easy to blow air in the fuel inlet with lung pressure. Turning the carburetor upside down so the float closes the needle it should hold off lung pressure and not allow any flow. That's pressure not too much different from a tractor's gravity flow from the tank.

I have a gas 4020, similar vintage with a Zenith carburetor. The first year it used 4 times the gas as my MF-135 had been using doing the same acres (but considerably faster) and it always had a cloud of black smoke out of the exhaust even when idling. When goosed the black cloud was much bigger, a lot like an IH diesel.

I went to the nearest green dealer to get needle and seat and mentioned how it was running, the parts counter suggested I talk to their gas engine expert in the south shop. With needle and seat in hand, I went to his office. After I described what it was doing, he said, "Until you replace the float needle and seat, I won't talk to you." The needle and seat did help a lot and the old one didn't pass my lung pressure test for shutting off. The end of the needle was visibly worn. I also found the choke cable wasn't opening the choke all the way because the sheath wasn't anchored near the carburetor, and I found mud dauber and wasp nests in the intake below the Donaldson Precleaner. Probably found a dirty air cleaner element too. I found the top of the Donaldson precleaner domed down instead of up and that was choking air flow to the engine too. All of those things plus copper wire to the plugs and I got rid of the black smoke and cut the fuel consumption a great deal, didn't get down to the MF-135 consumption but less than twice its fuel consumption for working the same acres faster. The gas 4020 was never known as a thrifty fuel user, from what I have found its nearly the lowest rated hp-hr / gallon at Nebraska Tractor Tests, the worst was an IH 685 hydrostat.

Gerald J.

Mack, it has electronic ignition. I also can tell that the starter is dragging a little, and I need to get it rebuilt. .maybe I should have had that done before I even posted this question. Needle and seat was at the top of my guess list but I figured that if that was the case, it would sit and leak gas all of the time; even when shut off, and while running. But it doesn't. I am going to get the starter rebuilt, and probably take the carb to a reputable rebuilder. Thanks, Darrel

Shhhh it, TREVMAN. I'd rather not hear that. Lol Darrel

Wouldn't hurt my feelings one bit to ditch the holley. What model zenith or other brand would work on there. .? Darrel

Sounds to me like you have two problems there Darrel. Those Holleys are an ass-ache to start off with. You'd be better off switching over to the Zenith replacement. Second, if you have a Starter dragging, that may be pulling a lot of power from the Battery making the Ignition side of the circuit weak, or causing a "low voltage" issue to the E.I. Most 12V E.I.'s need at least 8.5V to fire off the module. Low voltage will also take out the E.I. eventually if the issue isn't rectified. The P/N for the correct Zenith on that application I believe is a Zenith number 13303  (4021805).  I know I can help ya on the Starter for rebuilding, but I'd have to see if I have a Zenith Carburetor if your interested...
Steve@B&B 

if all of the above dosent do it because it said it does not leak when sitting i am leaning toward electrical and ignition ,       but if the intake valves are leaking a little the gas air doesnt make it to the cylinders .    if that manifold has a vacumm port you may try a little tuning with a vaccumm gauge