i dunno what you mean by _I have made sure the ground wire is attached_
try connecting the condenser directly to the magneto ignition-coil / points as previously outlined..
Then remove the plug, re-attach it's boot and solidly ground the plug's base to the engine fins.. Kick it over and observe spark. Another way would be to use some Starter Fluid and a install a new plug (or one known to be good), bypassing possible carburation troubles while confirming ignition is ok..