Ideal mexico super rs.65?

My problem is not with the pilot light stays a light without problem, my proble is with the main burner, when I go through the start up procedure and turn the thermostat switch up to 6 as specifed the burner then fires up but will only run for a few minutes before it cuts out and then will not start up again until it is left for a time possibly to cool down, I took one of the radiators off today for decorating purpose but I think this can only be a coincidence, any ideas welcome