What is the history of this carb, new, used, stored for long time? Floats / needles may be stuck. Maybe someone rebuilt it did not rough in the float level. Maybe a lot of things
Compression, spark and fuel. That is what you need to run
Compression--ENOUGH. A worn out engine low as say, 75 psi compression could run If the thing has gotten too much fuel it may have "washed down" the rings, lowering compression, and fouled the plugs..........check them. Wet or dry they will tell you a story
Spark.......good spark and at right time. "Rig" a test gap out of coil and use a solid core wire, even if you must use a low voltage wire "hung in space." Cranking WITH THE KEY you should get a nice hot snappy blue spark at least 3/8 and typically 1/2" long. TIMING. Spark must be in time. You can double check timing on the starter with a light It is likely OK
Fuel. Fresh fuel, not too much, not too little. Hell I've fired engines WITHOUT a carburetor, just throw a little down the intake throats, about a tablespoon.
