Another quiz

[MrSteele 482]

The tractor, not a Simplicity, but with a Briggs engine, 11 HP vertical shaft I/C, similar to any repower vertical shaft engines. It started, as usual, with the choke closed, ran a few seconds on choke, then moved the throttle control to operating range, came out of the shop, and died when I engaged the blades. It restarts easily on choke, but dies when the throttle is either moved, or not, from the choke position. Adjusting the carb got me through the yard, but the engine is puffing black smoke as if it is running rich, then easing into a prper running mode on occasion without me touching the carb. I know what it is, and it is a simple fix. Parts will have to be bought, and they are mentioned in another recent post, but for a different reason. Any takers?