If your starter was weak it may have been pulling to many amps to turn it over.....when it doeas that it takes juice away from the ignition circuit.....make sure the battery is fully charged and the new starter pulls low amps to turn it over.....

I have seen the plug spark outside the engine in these cases but thread it in the block and it wouldn't fire....

check the timing with a light while someone cranks the engine....see where your at....