BN carb.

[Mrfred54]

This tractor will not idle down. Had carburetor off and butterfly closes all the way. No intake leaks. Governor adjusted properly. Even unhooked the governor rod and hold the carburetor so the idle adjusting screw is held against the stop pin and still runs about half speed. Any suggestions???

 

[Jim Becker]

What happened when you backed the idle screw out? If not the adjustment, probably a vacuum leak. The leak could be at the carb-manifold gasket or manifold-head gasket. If not a gasket, you could have a rust hole in the manifold. Rust holes between the intake and exhaust sides of the manifold are not unheard of.

 

[used red MN]

Had carburetor off and butterfly closes all the way

I suspect you checked this but is the throttle plate centered in the carb bore so it can close completely? To center loosen throttle plate mount screws to the point where the plate can just move. Hold tension on the throttle shaft lever in the closed direction. Tap the throttle plate with the end of the screwdriver shank to center the plate and tight down the plate while continuing to hold pressure on the lever.

 

[Mrfred54]

I have sprayed either around the manifold and gaskets. No difference. Had the carburetor off twice and butterfly off the shaft. Butterfly will shut tight in the bore. Have to recheck everything a third time I guess, have never had this happen. Must be old age kicking in, I have worked on hundreds and hundreds of these tractors, I'm missing something, just gotta figure out what. Be awhile before I get back at it, got corn and beans to get in the ground

 

[DaveBN]

Does the throttle shaft fit tightly in the carb body or can you wiggle it back and forth or up and down? If the shaft is loose that could be your air leak.
Dave