I may add...
Make sure you are at top dead center at the top end of your stroke (intake), not top dead center on the downward stroke (exhaust). You can put a pencil in the spark-plug hole and watch it come up, and then down. You need to insure the pencil is at the top. If you do it based on the markings (per the book), you could inadvertently forget to make sure it was at the top, not the bottom.
I made the mistake and adjusted my valves incorrectly. It wasn't a major issue, just a royal pain-in-the-a$$ since you have to almost put it all back together to test it.
I got fed up and took it to the shop, it wasn't very expensive (around $150).
Good Luck !!