Farmall 400, Unable to adjust RPM with governor screw

My Farmall 400 is running at a lower RPM than it should (tach is broken, but I have estimated it at about 1300 high idle using a digital tach on the power steering pulley). A few weeks ago I noticed a lot of play in the speed control lever up at the steering wheel. I took the play out of that linkage so that the rod moves the linkages (on that side of the tractor) the way it should. However, when I try to adjust the engine RPM using the high idle screw in the governor, the governor does not react. I can turn that screw in or out almost all the way without the RPM changing. What might be causing this and what would be the next logical linkage or part to check for wear? Thank you for your time.

Sincerely,

Peter Markel

Have you followed up on all the good suggestions that were given on your thread of July 15 ? I think pete 23 had it nailed. Check out all the linkage
points between the throttle lever and the governor. Bob

Are you referring to the stop screw behind the governor housing side plate, lower one in lever that front spring eye attaches to? If the throttle linkage doesn't move the screw end to housing when it's backed out a little at a time you better check the throttle linkage to governor again. Or remove throttle rod at governor lever and pull it to rear by hand if screw doesn't contact housing to see if it does then. Probably the first thing to do besides checking the throttle linkage is check the carburetor shaft to governor adjustment for opening butterfly fully. Take the two screw cover with pipe tube lose. Under it with a original type governor is a pin with cotter key. Remove the pin. With throttle open and if you have side cover off check to see if lever that governor spring attaches to at rear is forward. Hold the short lever under the top cover up or to you, pin should just slide in without trying to force shaft and lever. If off loosen lock nut and adjust the yoke. If that adjustment is okay and it won't rev when operating the lever on rear of governor between it and engine to full back you have a real week spring or a problem with the governor its self. If that's the case some things to check can be added.
Throttle linkage is a common problem with those. From pin at throttle lever, pin at front of throttle lever rod in lever and pin or pins in levers on cross shaft in steering and tank support can be a problem. Think the throttle lever rod gets twisted also sometimes. Some tractors have had rod to governor length changed by welding. Same for vertical rod at steering and tank support. Also the adjustment joint is shot on the vertical rod. Find some with the front lever on hand throttle shaft made longer to move linkage more than original.

Does the power steering pulley turn the same rpm as the crank pulley? If not your estimate could be wrong.Mark

I think it does, but I am not positive so I also measured the belt pulley and PTO speeds which were both well below their rated No-load RPM.

Thank you for the advice. I ordered a new governor spring and throttle shaft linkage (I'll start with the spring and see if that helps). I know the throttle linkages are working to the governor itself and I check to see if the lever on the back of the governor is moving the vertical linkage beneath the breather tube to its full range and it appears that it is. However, I will run through the rest of your tips when I put in the new spring and see if the problem lies there. Thanks,

Pete.