Right I cant paste the page from the parts manual or e mail it to you as it wont let me also the part I think your missing isn't shown in any pictures of the exhaust valves or the barrels go in to the parts manual and go on the the link for the 21 and click on exhaust vavles and on cylinder head,the part does not show up.You could ask Andy if he has one or if Stephenrc45 has one.