It will be difficult, if not impossible to see a difference in the position of the throttle linkage when the engine doesn't return to normal idle- - - -we're talking about a difference of a few thousandths of an inch- - - - -at the throttle plates deep inside the carb. Bite the bullet, pull the carb, and adjust the centering of the throttle plates!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!