Scooterotica

Hi guys

I've had my side casing painted and the nugget who did it didn't mask out the threads on the filler and oil drain plugs.

I need to run a tap through them, but have no idea of the size. Can anyone offer advice please?

Many thanks
BOON

16mm x 1.5 pitch

Managed to sort it with a small wire brush from Wilko's and some grinding paste on an old plug.