Small Engines (Lawn Mowers, etc.): Riding La Craftsman Mod. 917.255740, carburetor problems, throttle valve

Question
I have a 20 year 0ld Lawnmower that has carburetor problems. A part, (spring or somekind of linkage) broke loose from between the throttle cable and carburetor while I was cutting our one acre field. I have no idea what this part is(nor could I find it), so I can't fabricate one myself.
I purchased a new carburetor and installed it, but it did not come with the part I needed. I fabricated a spring-type linkage and this allowed the throttle to move the output butterfly. But now, for some reason, unless the air intake "butterfly" is wide open, it won't start. Am I missing another part?
I understand how an automobile carburetor works, but I don't fully understand lawnmower carburetors. If I knew how the carburetor works, I know I can fix it.
Could you briefly explain how the the input and output "Butterflys" function.
Thanx for your help.
Al,  

Answer
Hello Al:

The Part Missing is the Governor Linkage (Metal) that Goes from the Governor Arm to the Throttle Valve Plate. Usually the Throttle Valve is Wide Open when the Engine is Not Running. When the Engine Starts the Governor Regulates the Speed through the Governor Linkage. This is what Returns the Throttle Valve to Idle. There is a Spring that Holds Any Slack that is Attached in the Same Holes as the Governor Linkage. You can View a Breakdown/IPL at this Site Addy, http://www.outdoordistributors.com/ and Select the T. Then Select Tecumseh. Then Select Don't have Part Numbers. The Enter the Model Numbers 143.366012. This is the Model Number of your Engine. The Governor Linkage and Spring are Shown on Page 1 of 10 and is # 186 (Linkage) and #186B (Linkage Spring). The Tecumseh Part Numbers are #186 (35302) and #186B (35346). Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

Good Luck

Respectfully

John