I am a curb trash scavenger also. Gasoline engines must have gas,
spark and compression to run. Most engine problems I've pinned down
have been no spark or low compression. This excludes the normal dirty
carb and dirt in gas tank.
Squirt a little gas right into the carb. (not in a closed area)
If that doesn't help. Check for spark.
If spark, check compression. Compression has to be above 70 psi. Lot
of times it will run with low compression and 1/2 to 3/4 choke but not
well.