Robert. Found you on FENA home page. Tonight I was using my tractor and just before I finished up the engine increased to max throttle and won’t idle down, and I am sure it is the governor. Is it a big job to take off and repair or install a used one or new or rebuilt? I have never worked on one before. April 13, 2015.
I would suggest you check the adjustment of the governor first, just to make sure it isn’t a matter of adjustment. I’d also check to make sure all the springs and linkage are in place. And, check the carburetor throttle shaft operation. A copy of the adjustment procedure is attached. You should be able to get the engine to idle by pulling back on the throttle linkage, the rod going to the carburetor, to force it into the idle position. If everything checks out it is likely your governor is to blame.
To remove the governor, remove the hood, drain and remove the radiator and the fan belt. Remove the crankshaft pulley, disconnect the governor linkage and remove the timing gear cover. If any of the balls on the governor are missing they usually can be found in the oil pan. Remove any balls that have dropped down into the oil pan. Check the control arm, particularly where it is pinned to the paddle that contacts the governor disc. The governor is not rebuildable.
You can purchase a replacement governor from numerous after-market sources. Make sure you follow the printed instructions that come with the replacement governor. The replacement governors use a shim, which is included, behind the governor ball assembly. The instructions should also include instructions about how to install the nut that holds the governor to the camshaft.
Those instructions usually indicate the shoulder on the nut should be installed facing the engine so the governor assembly is supported by the shoulder on the nut. Again, read the instructions carefully and follow them. Be careful when installing and tightening the large nut as it is very easy to break off the threaded end of the cam shaft. You should also install a new gasket before installing the timing gear cover.
Check the bearings and seal in the timing gear cover where the shaft for the control lever is attached. Replace these as needed. You will need to drill out the tapered pin that holds the paddle to the shaft. There are 2 needle bearings and a seal. You will also need a new tapered pin to replace the one that attaches the shaft to the paddle.
After reassembly, make sure you adjust the governor according to the attached procedure. The complete procedure can be found in either the original factory shop manual which is still available from AGCO/Massey Ferguson or in one of the aftermarket manuals. The procedure is the same for all the Z series Continental engines, Z120, Z129, Z134 and Z145 as used on the TE/TO-20, TO-30, TO-35, MF-35, F-40, MH-50, MF-50 and their industrial model derivatives.