Simplicity Regent 12 Briggs 289707 stuttering, runs rough, won't idle or throttle properly

Simplicity Regent 12 witha 12.5hp Briggs 289707 1 cylinder 4 stroke running incredibly rough, smoking, stuttering. On lower power settings it will smooth out for about 3-5 seconds then die, on high power settings it stutters and runs extremely rough, never smooths out. Has an integrated choke/throttle lever.
 
Replaced fuel filter and spark plug (it is sparking I checked), new fuel, tried starter fluid, sprayed carb cleaner (but it didn't look dirty), completely removed air filter. I did my best to adjust the throttle/ choke cables and make sure they would fully open/ close the choke as the choke lever is pulled but the 30 year old manual doesn't detail this well. When hand turning the engine (via the cooling fan) it does seem to generate some pretty modest compression.
 
It did run 2 weeks ago just fine. Anyone have any suggestions?

Many issues, with E Fuel now a days cause issues with the carb.
 
Pull it apart paying close attention to the internal jets:
 
https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/briggs-stratton/briggs-stratton-engine/200000-399999-series/289700-to-289799/289707-0154-01/carburetors-gasket-sets 
 
EVERY orifice must be clear.  I use brake cleaner on anything that has rubber (seals), carb cleaner 
on the carb body..    If you have an air compressor, use that too..
 
 
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Disassembled the carb and found that the jet was just floating free in the bowl and was not properly installed. Fixed that and it runs fine now.

That'd do it!  Happy mower'n
 
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