Engine runs at full throttle

[Frankie Harmon]

I have a briggs and stratton 17.5 hp model 31g777 type 0806 E1 code 070329zd on a craftmans riding mower. About 4 or 5 years ago while using it, it began to run at full throttle and we couldn't slow it down. We replaced the carburetor to no avail. We parked it until recently. A local mechanic listened to it and told us to replace the governor. The one we took out looked fine, but since we had a new one we replaced it and adjusted it as shown on several internet sites. It had no effect. Still running at full throttle. We tore down the motor. Replaced the rings. Cleaned the piston and head. Checked the valves. Everything looked good. Put it back together and on the mower. Still no effect.
Checked the carburetor and replaced the o-ring between the plastic intake tube or manifold. Still no effect. While the motor is running, we can put on the choke and it slows down some for a little while then speeds back up. What should we try next? We also tried to adjust the governor opposite the instructions just in case we are dyslexic. Evidently we are not dyslexic.

 

[bertsmobile1]

A racing engine is always the governor
So it has not been installed properly or is not connected properly
If it is installed properly with the engine stationary it will be pushing the throttle butterfly fully open
With the engine running if you push the governor lever to open the throttle it should push back against your finger with a fairly strong force.
Because carbs are a universal fit it is possible to hook the tie rod between the governor & the carb butterfly backwards so the governor opens the throttle in place of closing it as the engine speeds up