I have a model CH20S Simplicity garden tractor that runs at high speed only. I want to adjust the accelerator linkage and/or governor so that I can adjust the speed of the engine. It appears that a spring may be missing which pulls the governor closed so that it slows down the engine speed. Is there a diagram available to show what it should look like so I can determine if a spring is missing?

What brand and model engine does it have? Are you sure about that model #? Search / Simplicity (http://www.simplicitymfg.com/search/index.cfm)

It's a Kohler engine model CH20S. The tractor model is a Simplicity Sunstar Model 1692133.

Maintenance tips and manuals can be opened from this link Kohler Engines: CH640/CH20: Command PRO: Product Detail: Engines (http://www.kohlerengines.com/onlinecatalog/productDetail.htm?productNumber=Command%20PRO%20CH 20/CH640)

Hi, The manual is linked below (about 5MB):
"K&T Parts House Lawn Mower Parts and Chain Saw & Trimmer Parts" (http://www.mymowerparts.com/pdf/Kohler_Service_and_Repair_Manuals/)
Do not think that is it, but may be?
Peace,
Clarke