Hi David, Your a hero!!! I have been looking for a Vid to explain the timing on a 450 for over a year now. I built one engine and got the timing right by luck rather than judgment with probing the No 1 cylinder and guessing really. Your second Vid was a great help too with the sprockets and very well explained. Got one engine apart and ready for assembly and will walk into the workshop tomorrow a lot more confident thanks for to your help. Big Thanks Matty