Shaun , I think other people had mentioned about cleaning the tank out and I'm now going to flush mine out again. Just remembered how bad mine was when I first rebuilt the bike . You get all that work done and miss something so basic ! well at least I did ! Maybe just the fact that you want the bike to go and you get a blood rush or something. Mine had a considerable amount of fine dried dirt/metal that after the first run caused the rocker feed to block on my first run and I had a valve stick ,guite a push home . Stripped the top end changed a valve and all was well again .I had cleaned mine out and was convinced it was ok and clean but when I looked after the head had been done I found a considerable amount at the bottom which was at least an half inch deep . I had the tank power blasted and dried and then changed the oil at least 3 times to get the residual shit out of the system which fortunately did seem to clear it all out . So forearmed is forewarned thay'll be my job during this week ,best wishes BobH