3010 Zenith Carb Idle Problem?

63 3010 Gas with a Zenith Carb. After I bought this tractor I dialed in the carb adjusted the throttle and everything was fine for a while. Now it still runs good with higher rpm or a load but the idle is a little rough. I turned in the idle mixture screw and the idle improved. The idle mix screw is all the way in and it is still idling a little rich. I did a complete rebuild with a kit and I have the same problem? Could the load needle be affecting the idle mixture? Should I look at the points, distributor? I just can't figure out how the idle can be too rich with the mixture needle all the way seated? It shouldn't even run this way!

Any Ideas?

Thanks
 
Any chance that your choke cable has either become bent or has slipped on the carb, not pushing the choke all the way off?
 
Some carbs loosening the idle screw actually leans them.
I don't remember if that one is of this type.
 
I've got a diffeernt color tractor, but the idle screw on mine doesn't adjust more-or-less idle fuel, it adjusts more-or-less idle air. I turn mine just backwards to what I'd think.
 
I will double check the choke linkage. I took my time and was very thorough with the carb overhaul. Still possible there is something stuck in there.

I plan on replacing cap, rotor, plugs, wires, & points soon, just general mtx. I will try turning the load screw in an see if it responds any.

I will post back if this helps any or I find the problem.
 
As others have said... Believe that's an AIR adjusting screw. Fuel is metered via passageways and meteriing jets. The volume of iar mixed with that metered fuel is adjusted by this screw. Out leans it down by allowing more air in the final mixing stages of that carb.

Usually if an idle mixture screw meters fuel it is long and slender. If it meters AIR it is rather blunt with a steep taper. Like the difference between a drift punch taper versus the taper of a cold chisel grind.

Either get it running & back it out a couple or three turns to see what it does or look at the old one (from your kit) & see if it isn't a blunt nosed goober! If blunt nosed... back it out a couple or three turns & see what it does. Mine 3020 has a MS carb or I'd just look for ya.

Hope that helps.
 
These carburetors will run rich when they become worn in the accelerator piston and bore. You can replace the piston but the bore is what it is and may be worn too large to correct. DW
 

I think the piston and bore might be the culprit here. I talked with a guy that rebuilds these things. Said you should be able to kill the engine at idle by turning the idle mix screw all the way in. He also said any fuel leaking by the piston inside this carb will drive you crazy trying to figure out what is going on. Sorry but I still haven't had any time to mess with it other than verifying that the choke is full open.
 

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