Just a suggestion that doesn't appear to be covered in the thread. When setting the timing, the instructions are very 'monkey see, monkey do' and if the end result isn't what you hoped for, you may be flummoxed if unfamiliar with steam plant. If you adjust one end to sort a problem, how do you know that the other end isn't affecting the problem, at least in part and you end up chasing your tail?
My solution was to get the valve travel adjustment as accurate as possible. Then I slipped a spade blank cut from a drinks can between the block and cylinder inlet flange at one end. (Watch out you don't damage the gasket.) Thus with one end isolated, I could adjust the other until it was running as near-perfect as possible. Swop the blank to the other cylinder and repeat. Remove blank and the engine should be running at its best.
Barry M