At least I hope this is it because it's the only tangible problem I've
found so far. I received my replacement leakdown tester and the B&S
"L" head engine was the first test to see if it was working properly.

I had tried a crude compression test a while back that showed no
symptoms, but with the tester, I located a lot of leakage at the
exhaust valve (I could hear a lot of hissing at the muffler).

The symptom was hard to start and keep running, but once the engine
was warmed up, it would keep running at 1/2 choke eventually running
at 80% power with the choke full OFF.

I can only guess the valve and valve seat expanded as the engine
warmed up to where there was enough compression to keep the engine
running once it got hot. I can't do the valves for several weeks, but
once I do the valves and true the head, the engine should be running a
lot better.

My thanks to everyone for their help, tips, and suggestions. I leaned
a lot.

Manjo