My TO-35 began to “run away w/itself” last week. It revved so high it threw the belt off a 6′ finish mower. After checking the throttle linkage & looking at comments on the web, I think there is a problem with the governor. Parts have to be replaced. Is this a pretty safe bet? Parts are not too high – but it is a bit of a project.
Yes, it sounds like your governor needs to be replaced. Be sure to follow the installation instructions exactly for your tractor. The new replacement governors for the Continental gas engine usually include a shim that fits under the new governor and instructions about the placement of the nut that holds the governor to the camshaft. This nut must be installed correctly, usually with the turned down shoulder facing the governor assembly and supporting it.
Also be careful not to over torque the nut. It is easy to break off the threaded end of the cam shaft and then you will face the expense of replacing the camshaft. These changes in the replacement governor were made in order to allow it to replace the governor on both the Continental and Perkins gas engines.
Make sure you follow the procedure for adjusting the governor linkage once you assemble it. Adjustment is critical for proper operation. Make sure you check the condition of the two needle bearings in the cover as well as the seals. The bearings support the shaft that connects to the linkage arm.
You should also check the springs in the linkage. There are 3, one at the bottom of the plunger that contacts the arm connected to the governor dish or cup, one at the top of the plunger linkage, and one at the throttle linkage under the dash.
The governors sold by the after-market suppliers are usually the same as those currently being sold by AGCO/Massey Ferguson as replacements.