Hello! I have just bought one of these secondhand. Starting is difficult - it will go but stalls when the throttle is opened. The clutch is savage when you do get it revving. What is the little black handlebar lever mounted centrally - decompression or choke? It starts easier with it applied. Where should the fuel tap be positioned? Sorry for the torrent of queries and very grateful for any help here - my star is rather fading in my sonĀ“s eyes!