JLG 600A sputters and dies when hot - Gas Carburated

Starts fine, runs good until it gets hot (normally hot). Then, like light switch, it starts to backfire, runs rough, and stalls. On restart it continues to misbehave. If I wait until it cools off, all is good again. Takes about 20 minutes of running before it acts up.
I bought this used, and found someone had bent the choke blade...I thought that was it! But cleaned the carb and straightened the choke situation and same. It does start better now...
The guy I bought it from did disclose...

JLG 600A sputters and dies when hot - Gas Carburated

JLG 600A sputters and dies when hot - Gas Carburated