Running with the choke out

[Larry in GA.]

The Super C has started running real rough unless you run it with the choke out about 1/3 to half way. You can pull the choke out tell it smoothes out and run it all after noon jest fine.Try pushing it back in and it goes to running rough again. I have started leave it out and it starts right up and runs at that setting. Any ideas would be appreciated.
Larry

 

[CNKS]

The carb is too lean -- clean and put in a kit.

 

[ScottyHOMeY]

Probably a lean carb, needing a cleaning or euild.

Wouldn't hurt to doa visual and a wiggle first, to make sure the manifold is snugged up tight and hasn't developed a crack, and that the carb is snug up against the manifold.

 

[bn544]

i've got the same problem with my 544. i've been through the carb 3 times with 1 new kit and had the manifold off and put on a new gasket, still the same problem. one mechanic told me to go through the ignition system which doesn't make sense to me but i'm willing to try it just haven't got to it yet.

 

[El Toro]

Good indication of a lean carburetor. Need to
check the fuel system from the tank to carburetor.
Pull the gas line off at the carburetor and check for a good flow no dribble. Hold a clean container under the gas line and if there's a good stream check the strainer at the carburetor inlet. If its clean you need to pull the carburetor and soak in carburetor cleaner and blow out all passages. Then install a new kit. Hal

 

[teddy52food]

I would think the main jet has a small piece of dirt in it, causing it to run lean. If it runs a long time with the choke on part way, I think the fuel supply is OK.

 

[crate78]

Excess wear on the butterfly shaft in the carb can cause it to pull air in past the shaft resulting in a lean condition. We had this happen on a VAC Case once.

Since the carb body is cast and the butterfly shaft is usually brass, the shaft will usually wear instead of the carb body.

 

[Anonymous-0]

We had that with out skid steer. It was a combination of things in our case. Its definatly lean. But first several things can cause that. ANY way extra air goes in that the carb doesnt intend (by design) will lean it out. And if it runs with choke on that far its got a nice leak somwhere. Bad carb body gasket, cracked manifold, loose manifold or stripped/broken bolt etc etc. Check the entire system from block up is my recomendation cause anywhere along that entire intake system can be a issue. Old iron often cracks under stress. Metal gaskets deteriate etc. In our case it was cracked manifold, loose bolt (as a result), and ALL bad gaskets some leaking more then others. Gaskets are cheap. Best to replace them and rebuild or atleast clean carb and set float height (also check float for squareness to carb body).

 

[Anonymous-0]

In your case, if it were me I would check fuel delivery AND fuel pump presure (use a T and presure gauge from fuel pump output). If you find fuel flow is low, then it can be several things also of which were listed earlier by others (tank screen, fuel filter etc etc)

 

[Brownie450]

Try raising the float level just a bit--not much & see how it runs then. Our SC had to be adjusted 3 times to run right.

 

[otherhalf]

Hi all. When I plow snow with my cub, it sometimes does the same thing. I can run it with the choke on. I clean the sediment bowl and screen and it runs fine. Just another thought.

 

[Anonymous-0]

What I'd try first do a diagonistic test using WD40 or carb cleaner (don't use ether if you like your eyebrows) and ensuring that the intake tube is good and snug on the carb give a quick light shot all the way around the carb base, intake manifold and the gasket area to include the backside. DON'T STATURATE IT!!! If you have a leak, it will straighten out and take off for a second. I doubt you have an air leak though. I'd think it's junk in the fuel/fuel lines/carb so I'd check fuel flow and make sure you don't have any junk in there first. Good luck

 

[jonnny2006]

time for a carb kit. also do a flow test..

 

[A. Bohemian]

None of the suggestions above are out of line. They are all sound advice.

For me, though, it"s all about TIME. I want to fix things as quickly as possible.

In order to do this, it is necessary to ISOLATE the source of the problem BEFORE adjusting, replacing, etc., etc., otherwise one is dependent on luck.

I also like to do the quickest checks first. Here, I think the fastest one is going to be squirting something suitable around and look for air leaks as described above.

After that, I would do a fuel flow check, especially if this tractor is kept outdoors when not in use. Pull the plug and look for a STEADY stream about the diameter of the plug. Let it flow for several minutes.

If the fuel flow checks out ok, I would run a spark test before going on.

(Yes, I KNOW it is counterintuitive. But weak spark CAN cause an engine to run much better with the choke applied.)

Make one of Dell"s calibrated spark testers. Get a good plug and bend the electrode out to 3/16"". Clamp it to ground. Remove ONE spark wire at a time and connect it to the test plug.

You want to see a nice, wide, bright blue spark. Weak or discolored spark is suspect.

Because rebuilding the carb is such a time consuming method FOR DIAGNOSES PURPOSES, it is last on my list. First I try to demonstrate to myself that the carb IS the problem.

The best way to isolate the problem to the carb is to substitute the one you have with a known good one. Not always practical, but I always like to mention it in case you are lucky enough (as an I) and there are still several Cs in use in your neighborhood.

Barring that, I have had good luck over the years on a wide variety of vehicles with the following approach, which will isolate a bad carb almost every time:

I try to tune the carb in accordance with the instructions in the shop manual. If the carb fails to respond to any of the adjustments, be suspicious of it. I"m not saying all the adjustments need to be able to make the tractor run perfectly; remember, we are still diagnosing at this point and the carb MAY NOT be the problem!

But you should generally see SOME KIND of response to each adjustment when performing the carb adjustment procedure in the shop manual.

Good luck. It will be greatly appreciated if you keep us posted so that we may learn from your experiences.

 

[georgeky]

How many gas Farmall tractors have fuel pumps? None that I know of.

 

[Anonymous-0]

It was intended as a general guide (not model/brand specific). No pump, no biggy you can still test fuel flow, you just wont have the presure to test like a pump would is all. Nice flow, all go-trickle and its in need of checking over.