Hi guys. I took the head off my newly aquired erst. Knowing that it had been running rich and low on oil i wanted to see what pistons were like. From what I can see they look ok just coked up. However the valves in my head are solid. Its like they have a lump of cement on each valve. Whats the best way to clean these up. please dont say some fine wet and dry because that wont cut it lol.

Is it ok to try and get off with screwdriver of will that damage them?