Valve seating @ valve gap clearences

As I mentioned 'I could of bought a brand spanking new head for next to nothing but the problem I had years ago with a Chinese motorcycle they tend to not start cause the valves tend to dig them selfs deeper into the valve seat and the valve clearnce will not be inspec.Make shore before you buy a usted head to check in a criss cross pattern with a steel ruler to make shore it's not warped from heat.Ther is a service limit of 0.05mm and check the journals wher the camshaft is seated for grooves