The valve is off center because of the worn guide. Those marks look like where the plating or the case hardening has been worn off by the keepers. That should not happen. Counterfeit part? Hardening or plating prob?
A spring removal and valve inspection at 500, 1500, 3000, 5000 miles would be a good idea on the fresh motor. Pack nylon rope into TDC cylinder, couple hours
These motors were engineered with the valves lubed by lead in the fuel. USA fuel has friction modifiers in it to replace the lead somewhat, probably not allowed in EU fuel. Add Hapco lead substitute, a $50 gallon treats 200 gal gas
A Howard Cams 93360 11/32- .530 type seal with a band instead of spring would form a hydrodynamic seal allowing oiling where a spring seal will wipe off
oil and stop oiling
I’m using the no band 3/8” - .530” 93320 Howard Ultimate seal, the 11/32” 93311 has .500 guide, these seals
oil the valves too.