Hi, can someone please help? i have a sears LT36 tractor made in the 70's. it ran fine until this spring. i beliebe it is a carb issue. it revs really high and no response to the throttle. first, i see three adjustable srews, the very top for the idle (only makes the speed higher when adjusted, the middle (maybe air?) and the one at the bottom with the bowl. can someone please help me? i did spray the carb but never took out the bowl screw. does anyone know the screw turns for all three or how i can fix the problem? thanks very much.

 

Adjusting the idle screw and causing it to rev higher does not make sense. The rest of the symptoms sounds like the throttle valve may be hung open in the carb throat.
Remove the air filter and you should be able to see the butterfly/throttle valve. You should be able to move it freely by hand. It should also respond to throttle movement when the engine is running, but may not with the engine off.
It could also be an intake leak, but I would expect some response to throttle.
Verify the throttle valve, and note any more info on adjusting the idle screw...

 

sounds like you have a broken governor spring or something has come lose in the linkages, check all the springs and stuff.