Small Engines (Lawn Mowers, etc.): B&S 18.5 HP engine doesnt speed up using throttle, briggs and stratton, throttle linkage

Question
Good Evening!
I have an MTD tractor with an 18.5 HP engine (Model 42A777, Type 1270-01, Code 9502035A.)
When advancing the throttle, the engine does NOT speed up.
I've taken apart the throttle linkage assembly, cleaned, and re-lubed it; checked and adjusted the carb to specs. Carb is very clean and had some additive applied, and works consistently well. When it's manually opened, the engine operates properly.
The only thing I haven't worked with is the governor, although it looks as if it's operating correctly. (I'm hesitant to try to adjust it, since it's generally a "no-no" to do so, it having been set at the factory.)
Therefore, throttle linkage OK, carb OK, could the governor be the problem?
Appreciate any help you can give me with this problem. (We're in the woods, but the weeds are growing....)
Thanks,
Jane


Answer
Hello Jane:

Has the Throttle Control Spring Broken? This is the Spring that Pulls the Governor Arm when you Move the Throttle Cable. Is the Throttle Cable Broken. When you Move the Throttle Lever, Does the End at the Carburetor Control Bracket Move? You can View a Breakdown/IPL of the Engine at this Site Addy, http://www.outdoordistributors.com/ and Select the B. Then Select Briggs and Stratton. Then Select Don't have Part Numbers. Then Select the File #42.  Then Select the Folder #42A700. When you Move the Throttle at the Carburetor you can Feel the Governor Push Against you as you Rev the Engine. If this Is Happening, then the Governor is Fine. It Will Not Stop the Engine From Revving, Just Over Revving. Hope this Helps. I am Here if You Require More Assistance. Let Me Know What Happens, Please. Thanks.

Good Luck

Respectfully  

John