"awesome" KB 107 surprise
ok, they did not cut the reliefs deep enough it looks like.
Look at the bottom of the pistons and tell me if you have 'made in mexico', 'made in the USA' .
Then weigh them all 1 at a time and tell us how far off in weight they are.
If you have some of both mex/us pistons, you'll notice that the mexico pistons weigh a lot more to the tune of 8-9 grams.
I'll post pics of my KB243's and there valve reliefs to ease your mind.