Hi If you are still with the cooker then DO NOT attempt to remove the lid, it has a gas switch control attached. 
Although your number is odd I have a NEW WORLD CKG 218 series and the gas switch was getting old. MY attempt to solve the problem took me a long time, only to replace the lid in an open position for the rest of its life.
                
 DIY - obsessive - Try Try again and get an expert in
                
 February 2011