There’s a lot of techniques for lapping valves. I find that the suction cup and stick works really well. The trick is how to test to make sure that everything is proper. First, use the water test. You make the head level, then screw in a spark plug upside down, and then pour water over the valves. Let it sit. You can put some toilet paper inside under the valves, and if anything leaks through, then you've got some more work to do. I like this method because I can do it BEFORE putting the springs on.

lapping valve tool kit: https://amzn.to/33ALPI5

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