It was running, but not real well, until points and wire from coil to points melted. Replaced plugs, points, condensor, coil, the melted wire, cap and rotor, as well as timing gears and chain. It seems to want to start but won't run for more than 20 seconds. Will be replacing carburetor soon. Any other ideas?

 

If I understand your description correctly, check the charging system or voltage from ign sw to coil. Could be sending 12 volts to coil all the time or charging system is running away at maximum voltage.