Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Take the slide valve and cover completely off .
Remove safety valve and blow into Safety valve hole with a rubber tube etc .
Air should freely escape from slide valve area .
If it does then steam line clear . If not then the steam line blocked.
The new bit you made did you have both broken bits to start with .
I suspect the replacement could be not quite right length 

Cheers
Dennis