if theres a little bit of black smoke coming out when you rev it up, i just rejetted and it runs fine, i did a plug test, perfect color light brown or so. just when i rev it up just a little bit of black comes out.
They can be, but don't have to be. I've tried it both ways and haven't really seen one way any better than the other. I just tweaked them until it ran better, whether it was offset a half turn or equal.