I did the old "I'll remeber where that goes" and forgot which crankcase dowels get an O-ring. If you have the parts diagram I can figure out where #21 and 20 go but I have another dowel with an O ring on it and can't find it in any diagrams. I know I left the O ring the dowel to at least be sure that it had one when I went for re-assembly. I should no better by now I'm a big boy now!!