Solution : https://service.sap.com/sap/support/notes/156597 (SAP Service marketplace login required)
Key words : 
additional key words co08, prerequisites solution implement, primary product item, sales order item, valuated sales order, primary product, sales order, production order, header material, settlement rule
Related Notes : 
       
| 314948 | Bill of material information in co-product item | 
| 301035 | CO07: Settlement rule for sales order | 
| 175431 | CO01,02:Manuf.of co-prod. & engineer-to-order prod. | 
| 160209 | Manufacture of co-products: settlement rule |