There are two levers on the handle of the mower. The gearshift handle and the throttle handle. To start with, I removed the spring. It appeared that the coils of the spring was rubbing against this plastic piece on the choke shaft. (I'll see if I can take a picture of the carb and choke). The throttle handle has three positions: slow, fast and choke. When the throttle is in the fast position with the spring removed, the choke is forced open all the way by the throttle linkage. The choke plate is not free to move by hand at this point. When the throttle lever is in the choke position, the choke plate is free to move by hand all the way to the close position and back to about 50% open. On this mower, the choke has to be 100% closed for the engine to start on a couple of pulls. The only way that can happen is if the spring pulls the choke closed. However, the choke is not closing on it's own. I can push lightly on it and it will close. When I place the lever in the 'fast' position, the choke will be 100% open. This mower has never been in the shop in 30 years. Never had a problem with starting. Never had the need to even look closely at the carb.Did not even know there was a spring on the choke plate assembly. I have replaced the pull-start assembly once but never had an issue with the carb. I need to see an actual B&S engine or a picture of one showing the choke assembly with the spring. I have a couple of new springs ordered. Will be in touch.
Thanks for the help
ctg