Hi there, I have recently purchased a suzuki DR250S, 1991 model. I know, it is an old bike but I thought it was good. It is road registered, which save the hassle of getting unregoed bike blue slipped, etc. Anyway, I did a bit of the service on this bike - changed sprocket, chain, clutch cable, spark plug, oil and oil filter. The bike was running fine before I serviced it, i.e. first kick start, no engine noice, simply a beauty! The oil that was in the bike was more like wax - very black, very dense! Once I replaced oil and filter, put new oil in it (15/50 i chose because the bike is old and thought needs heavier oil. Recommended is 10/40). So once I put new oil, started the bike (again first kick), there was massive rattling noise coming out of the engine. Massive! This noise was definitely not there before I changed oil/filter???? Any particlar reason(s) for this?? Have I done something wrong?? I put recommended 1700 ml of oil? Is this too much?? Not enough?? Or is it possible that the old, black, thick oil, was preventing the rattle??? Any help, ideas, suggestion, PLEASE!!!!!!